Vol.
174,
3, 1991
No.
February
BIOCHEMICAL
AND
BIOPHYSICAL
COMMUNICATIONS
RESEARCH
1318-1323
Pages
14, 1991
BILATERAL HYDROPHOBIC ZIPPER AS A HYPOTHETICAL STRUCTURE WHICH BINDS ACIDIC RIBOSOMAL PROTEIN FAMILY TOGETHER ON RIBOSOMES IN YEAST SACCHAROMYCES CEREVISIAE Kunio Department 1110
Tsurugi
and Kazuhiro
Mitsui
of Biochemistry, Yamanashi Medical Tamaho, Yamanashi, Japan 409-38
College,
Received January 9, 1991 Acidic ribosomal protein family of yeast Saccharomyces cerevisiae consists of four species of 13-kDa proteins and one species of 38-kDa protein. These proteins are thought to form a complex on ribosomes functioning in the translational elongation reaction, but the structural basis how to associate with one another is not known. In this communication, we show for the first time the presence of a structure equivalent to the leucine zipper on a putative alpha-helix in the 38-kDa acidic ribosomal protein, AO. Then, all the 13-kDa acidic ribosomal proteins are shown to have two periodic arrays of hydrophobic amino acid residues arranged on the opposite sides of a putative alpha-helix, which is referred to as the "bilateral hydrophobic zipper". Therefore, it is proposed that one of the 13-kDa acidic ribosomal proteins associates with 38-kDa protein A0 via the hydrophobic zipper and then the other 13-kDa proteins associate side by side via the bilateral hydrophobic zippers. 0 1991Academic Press,Ire. Yeast
Saccharomyces--
ribosomal
proteins
proteins about
which
L44'
acidic
elongation
share
13-kDa
residues
antibodies
against
synthesis
domain of
yeast
L7/L12
factors
and one 38-kDa sequence
proteins,
are
(1).
proteins
0 1991 by Academic Press. Inc. of reproduction in arty form reserved.
because
Therefore, is presumed
1318
of
named Al, to -.T E
involved
in the
The carboxy-terminal
not
carboxy-terminus
0006~291Xi91$1.50 Copyright All rights
as they
synthesis.
acidic
to be homologous
carboxy-terminal
in vitro -~ 13-kDa
thought
homologous
chemically-synthesized
protein
of
has been shown to be involved
elongation the
13-kDa
The 13-kDa
are
of protein
a family
carboxy-terminal
(1).
protein
proteins
with
four
a homologous
ribosomal
interaction
the
of
and L45 (2-4),
reaction
domain of
possesses
consisting
40 amino acid
A2(L44), coli
cerevisiae __ --.. __-
only
in the
(5)
but
decapeptides the to
the
also
inhibit
amino-terminal be involved
in
the
Vol.
174,
No.
association
with
protein. with
BIOCHEMICAL
3, 1991
The the
one
was
ribosomal
proteins
ribosomal the
acidic
further
to
rihosomal
their
is
in
hydrophobic
the that
because with
(8).
In
primary zipper
domain
every
protein
on a putative
ribosomal
thought
to
a human
a rat
13-kDa
with
one another,
to
and report leucine
acidic know
how
we that
zipper
some DNA-binding
possesses
A0
A0 homologue
report,
the
associate
acidic
this
to of
acidic
to
structures
similar
COMMUNICATIONS
13-kDa
cross-linked
associate
13-kDa
is
and because
dimerization
zipper
A0 (6),
(7)
proteins
a hydrophobic
and
solution
RESEARCH
38-kDa
a complex
be chemically
investigate
found
form
on ribosomes
contains
(9,lO)
to in
proteins
named
the
on ribosomes,
reported
demonstrated
BIOPHYSICAL
and with
protein,
proteins
homologue
was
another
39-kDa
13-kDa
AND
A0 which
proteins
a bilateral
alpha-helix.
MATERIALS
AND METHODS
The amino acid sequences used are AO, Al, A2, L44' and L45 from S. cerevisiae (2-4, 61, and PO, PI and P2 from human liver (7). Thesequence analysis was done using the computer programs in software DNASIS (Hitachi Software Engineering Co.).
RESULTS The and myself protein
amino
acid
sequence
the
nucleotide
from A0 is
312
AND DISCUSSION of
A0 was sequence
amino
acid
residues
205
TDEE
LVSHFVSAVS
229 255
Vp;apS II ii YHVPE[ED
tGI&NtK I*
deduced
ZVD~~E~PE~, II xx
of in
in
its
cDNA
length
and
TIASIS~AIC xxxxx*Ix D[LAVAIA[S XXIX YlYl V~AAA~AATS *ix* XI
by Mitsui
1988
(6).
Predicted
contains
228 254 282
Fiq.1. Repeated structure and periodic appearance of aliphatic amino acid residues in a domain (residues 205-282) of 38-kDa acidic ribosomal protein A0 from yeast 5. cerevisiae (6). Amino acid seauence is shown with sinale-letter abbreviations. The aliphatic amino acid residues that comprise the putative 1 marks identical amino acid hydrophobic zipper are boxed. residues and * marks residues with conservative change. The last line in the figure indicates the similarity between the first and Numbers indicate the the third segments of amino acid sequence. positions of the amino acid residues starting at the aminoterminal methionine. 1319
some
Vol.
174,
No.
3, 1991
BIOCHEMICAL
AND
BIOPHYSICAL
RESEARCH
COMMUNICATIONS
(b)
(a) Al
(106)
A2(106)
L44'(106)
1234567
L45(110)
1234567
1234567
12345
6 A G A V VD EL G
I Y G A A
K
Fiq.2. Helical wheel analysis (9) of the amino-terminal halves (residues I-49) of the 13-kDa acidic rihosomal proteins from yeast 2. cerevisiae which are classified into PI-type proteins, Al and L44' (a), and P2-type proteins, A2 and L45 (b). Strengthened letters indicate hydrophobic amino acid residues and numbers in the parentheses indicate total numbers of amino acid residues in the proteins. Conventionally, the amino acid sequence is aligned in segments of seven amino acid residues (above) and the positions of the arrays containing the putative hydrophobic zippers (boxed) are marked on a helical wheel (below). characteristic 252)
domains
which
Out of
(11).
corresponds
to
the
in position
is
to be composed of
three
with
of
residues
Of particular of
interest
aliphatic
the
domain
residue of
domain of A0 is region
not
zipper
shown).
containing
in binding
raises
proteins
also
associate
with
Thus,
the
residues a typical
a possibility have
seventh
a leucine
that
helical
zipper
AO. 1320
from
in the if
except
possesses
the
appearance
the
whole
The secondary
1).
leucine
25 1).
position
LLLLAIIA,
which
(Fig.
the
results
second and third
A0 probably
than
carboxy-terminus
however,
zipper,
generally
205-
13-kDa
one another
which
(Fig.
of
to Chou and Fasman (12)
including
alanine
activity
finding
according
is,
every
225,
an alpha-helix
that
(data
at
(residues
of a segment of about
50% to
domain
leucine
analysis
containing
about
half
homologous
repeats
at position
structure this
the
residues
an elongated
constitutes
to
in this
amino acid
leucine
formation
relative
a similarity
a domain
amino-terminal
proteins found
them,
is
predicts for
residues
an atypical
leucine
zipper acidic
or a similar
proline
leucine
expected
13-kDa
the
to be lower
(9).
This
ribosomal structure
to
Vol.
174,
No.
3, 1991
BIOCHEMICALAND
COMMUNICATIONS
(a)
(b) Al
1>44' PI
Cc) A2
P2
Fiq.3. Conservation of the amino acid residues which comprise the hydrophobic zippers in yeast and human acidic ribosomal proteins; proteins (c). The amino acid PO- (a), PI- (b) and PZ-type residues comprising the hydrophobic zipper are boxed. Numbers indicate the positions of the amino acid residues. Ribosomes acidic
13-kDa
PI-type the
(Al
from
ribosomal and L44')
heterogeneity
whether
they
amino acid analyzed
by helical
of
is
proteins
zipper
the
on a putative
(Fig.
and L44',
are
residues
as the
leucine.
It
is
of
particular
interest
opposite
sides
of
a putative
alpha-helix
hydrophobic also
zipper.
Similarly,
shown to possess
putative
alpha-helix
the
total
the
positions
different
a bilateral (Fig.
amino acid of
between
proteins
must
proteins
because
be
the
residues residues
them. lower the
2a).
The PI-type
shown to have two
they
between comprising
contain 1321
refer
residues
besides
on the
"bilateral" A2 and L45,
due to
on a
(106
zippers
than
more alanine
are
the difference
A2 and L45
zippers
activity
to
because
zipper
the
or
zipper"
locate
proteins,
Probably
in binding
five
we like
forming
The hydrophobic
formers
have been
hydrophobic
2b).
their
halves
amino acid
P2-type
based on
structure,
"hydrophobic
that
into
To examine
(1).
Here,
hydrophobic
of
classified
containing
alpha-helix.
structure
composed of various
half
(9)
amino acid
are
species
(A2 ans L45)
amino-terminal
Al
four
or a similar
analysis
proteins,
hypothetical
which
amino-terminal
wheel
hydrophobic
residues
it
of
contain
(l-4)
and P2-type
sequences
arrays
the
proteins
have a leucine
ribosomal
to
S. cerevisiae -~-~
in the
acidic
seven
yeast
of
and
in IIO),
are P2-type
those
of
residues
PI-type and
Vol.
174,
No.
one of
3, 1991
the
proline.
zippers
According
amino-terminal to
containing most
of
region.
to
the
proline
these
it
of
side.
13-kDa
This
idea
that
the
were
released
salts
ribosomal
depending
on various
hydrophobic
zipper
leucine
zipper
exchange
may be more
with
So far, primary
those
has
or 3a).
phobic completely
substituted
in
the other
partly
hydrophobic a putative three-residue
hydrophobic with
yeast
idea
PI-type in
that
hand,
they
however,
conserved zipper
in of
zipper
human
amino
(Fig.3c). is
long
acid This
enough 1322
than
to
PO, the
whose amino
A0 are
bilateral
This the
are
almost further
hydrophobic of
may comprise
human
acids hydro-
finding
zipper
residues
acid
either
amino
ribosomes
zippers. yeast
A2 is
a bilateral
on each
may be interpreted in
a typical
and L44')
hydrophobic P2 which
yeast the
proteins
in
3b). via
13-kDa in
A0 homologue
(Al
associate
of
(14-16).
the
(Fig.
the
three
alpha-helix
Pl
ribosomes
of
hydrophobic
proteins
human
liver
Furthermore,
In
constituting
results
ribosome
zipper
similar
by
concentration
the
only
a side
previous
be weaker
(7).
will
make
copies
pool
the
to
rat
of
for
reported
those
conserved
supports On the
the
also
(14).
to
that
zipper
low
a mole
a cytosolic PO is
been
Similarly,
zipper
to
expected
in
a helical
as nine
convenient
protein
constituting
conserved (Fig.
free
human
structure
residues
is
in
the
conditions
which
are
of
in
as many
bound
growth
probable
by the
even
to
proteins
is
associating
proteins
50% ethanol
are
it
hydrophobic
indirectly
three
proteins region
proteins
ribosomal
the
(12),
the
to A0 but
ribosomal
acidic
that
the
bind
supported
with and
(13)
acidic
is
13-kDa
to
acidic
acids
of
acid,
and Fasman
Therefore,
location
COMMUNICATIONS
amino
including
amino
only
RESEARCH
ribosomal
alpha-helix residue.
not
Chou
acidic
hydrophobic
possible
network
of
13-kDa
in
BIOPHYSICAL
by a neutral
method
of
The bilateral
make
only
interrupted
be rich
the
AND
is
halves
predicted
the
BIOCHEMICAL
side
of
as
that
since
some
Vol.
174,
No.
structural
3, 1991
BIOCHEMICAL
changes
a different
site
amino-terminal
have of
To resolve
experiments
are
developed
being
BIOPHYSICAL
during
P2 protein,
sequence,
association.
AND
these
the
well
participate
problems,
COMMUNICATIONS
evolution.
possibly
may also
RESEARCH
in
further
Alternatively, conserved their analysis
and
undertaken. REFERENCES
Tsurugi,K. and Mitsui,K. (1959) Biochem.Arch. 5, 211-221. Mitsui,K. and Tsurugi,K. (1988) Nucl.Acids Res. 16, 3574. Mitsui,K. and Tsurugi,K. (1988) Nucl.Acids Res. 16, 3575. Remacha,M., Saenz-Robles,M.T., Vilella,M.D. and Ballesta,J.P.G. (1988) J.Biol.Chem. 263, 9094-9101. 5. Uchiumi,T., Traut,R.R. and Kominami,R. J.Biol.Chem. (1990) 265, 89-95. 6. Mitsui,K. and Tsuruqi,K. (1988) Nucl.Acids Res. 16, 3573. 7. Rich,B.E. and Steitz,J.A. (1987) Mol.Cell.Biol. 7, 4065-4074. 8. Uchiumi,T., Wahba,A.J. and Traut,R.R. Proc.Natl.Acad.Sci.USA, 1 . 2. 3. 4.
(1987)
84,
5580-5584.
9. Landschulz,W.H., 240,
lO.Murre,C., ll.Mitsui,K.,
Johnson,P.F.
and McKnight,S.L.
(1988)
Science,
1759-1764.
McCaw,P.S. Nakaqawa,T.
and Baltimore,D. and Tsurugi,K.
(1989) (1989)
Cell, 56, J.Biochem.
777-783. 106,
223-227.
and Fasman,G.D. (1978) Ann.Rev.Biochem. 47, 251-276. 12.Chou,P.Y. 13.McConnel1,W.P. and Kaplan,N.O. (1982) J.Biol.Chem. 257,5359-5366. 14.Saenz-Robles,M.T., Remacha,M., Vilella,M.D., Zinker,S. and Ballesta,J.P.G. (1990) Biochim.Biophys.Acta, 1050, 51-55. 15.Zinker,S. and Warner,J.R. (1976) J.Biol.Chem. 251, 1799-1807. lG.Mitsui,K., Nakaqawa,T. and Tsurugi,K. (1988) J.Biochem. 104, 908-911.
1323
174,
3, 1991
No.
February
BIOCHEMICAL
AND
BIOPHYSICAL
COMMUNICATIONS
RESEARCH
1318-1323
Pages
14, 1991
BILATERAL HYDROPHOBIC ZIPPER AS A HYPOTHETICAL STRUCTURE WHICH BINDS ACIDIC RIBOSOMAL PROTEIN FAMILY TOGETHER ON RIBOSOMES IN YEAST SACCHAROMYCES CEREVISIAE Kunio Department 1110
Tsurugi
and Kazuhiro
Mitsui
of Biochemistry, Yamanashi Medical Tamaho, Yamanashi, Japan 409-38
College,
Received January 9, 1991 Acidic ribosomal protein family of yeast Saccharomyces cerevisiae consists of four species of 13-kDa proteins and one species of 38-kDa protein. These proteins are thought to form a complex on ribosomes functioning in the translational elongation reaction, but the structural basis how to associate with one another is not known. In this communication, we show for the first time the presence of a structure equivalent to the leucine zipper on a putative alpha-helix in the 38-kDa acidic ribosomal protein, AO. Then, all the 13-kDa acidic ribosomal proteins are shown to have two periodic arrays of hydrophobic amino acid residues arranged on the opposite sides of a putative alpha-helix, which is referred to as the "bilateral hydrophobic zipper". Therefore, it is proposed that one of the 13-kDa acidic ribosomal proteins associates with 38-kDa protein A0 via the hydrophobic zipper and then the other 13-kDa proteins associate side by side via the bilateral hydrophobic zippers. 0 1991Academic Press,Ire. Yeast
Saccharomyces--
ribosomal
proteins
proteins about
which
L44'
acidic
elongation
share
13-kDa
residues
antibodies
against
synthesis
domain of
yeast
L7/L12
factors
and one 38-kDa sequence
proteins,
are
(1).
proteins
0 1991 by Academic Press. Inc. of reproduction in arty form reserved.
because
Therefore, is presumed
1318
of
named Al, to -.T E
involved
in the
The carboxy-terminal
not
carboxy-terminus
0006~291Xi91$1.50 Copyright All rights
as they
synthesis.
acidic
to be homologous
carboxy-terminal
in vitro -~ 13-kDa
thought
homologous
chemically-synthesized
protein
of
has been shown to be involved
elongation the
13-kDa
The 13-kDa
are
of protein
a family
carboxy-terminal
(1).
protein
proteins
with
four
a homologous
ribosomal
interaction
the
of
and L45 (2-4),
reaction
domain of
possesses
consisting
40 amino acid
A2(L44), coli
cerevisiae __ --.. __-
only
in the
(5)
but
decapeptides the to
the
also
inhibit
amino-terminal be involved
in
the
Vol.
174,
No.
association
with
protein. with
BIOCHEMICAL
3, 1991
The the
one
was
ribosomal
proteins
ribosomal the
acidic
further
to
rihosomal
their
is
in
hydrophobic
the that
because with
(8).
In
primary zipper
domain
every
protein
on a putative
ribosomal
thought
to
a human
a rat
13-kDa
with
one another,
to
and report leucine
acidic know
how
we that
zipper
some DNA-binding
possesses
A0
A0 homologue
report,
the
associate
acidic
this
to of
acidic
to
structures
similar
COMMUNICATIONS
13-kDa
cross-linked
associate
13-kDa
is
and because
dimerization
zipper
A0 (6),
(7)
proteins
a hydrophobic
and
solution
RESEARCH
38-kDa
a complex
be chemically
investigate
found
form
on ribosomes
contains
(9,lO)
to in
proteins
named
the
on ribosomes,
reported
demonstrated
BIOPHYSICAL
and with
protein,
proteins
homologue
was
another
39-kDa
13-kDa
AND
A0 which
proteins
a bilateral
alpha-helix.
MATERIALS
AND METHODS
The amino acid sequences used are AO, Al, A2, L44' and L45 from S. cerevisiae (2-4, 61, and PO, PI and P2 from human liver (7). Thesequence analysis was done using the computer programs in software DNASIS (Hitachi Software Engineering Co.).
RESULTS The and myself protein
amino
acid
sequence
the
nucleotide
from A0 is
312
AND DISCUSSION of
A0 was sequence
amino
acid
residues
205
TDEE
LVSHFVSAVS
229 255
Vp;apS II ii YHVPE[ED
tGI&NtK I*
deduced
ZVD~~E~PE~, II xx
of in
in
its
cDNA
length
and
TIASIS~AIC xxxxx*Ix D[LAVAIA[S XXIX YlYl V~AAA~AATS *ix* XI
by Mitsui
1988
(6).
Predicted
contains
228 254 282
Fiq.1. Repeated structure and periodic appearance of aliphatic amino acid residues in a domain (residues 205-282) of 38-kDa acidic ribosomal protein A0 from yeast 5. cerevisiae (6). Amino acid seauence is shown with sinale-letter abbreviations. The aliphatic amino acid residues that comprise the putative 1 marks identical amino acid hydrophobic zipper are boxed. residues and * marks residues with conservative change. The last line in the figure indicates the similarity between the first and Numbers indicate the the third segments of amino acid sequence. positions of the amino acid residues starting at the aminoterminal methionine. 1319
some
Vol.
174,
No.
3, 1991
BIOCHEMICAL
AND
BIOPHYSICAL
RESEARCH
COMMUNICATIONS
(b)
(a) Al
(106)
A2(106)
L44'(106)
1234567
L45(110)
1234567
1234567
12345
6 A G A V VD EL G
I Y G A A
K
Fiq.2. Helical wheel analysis (9) of the amino-terminal halves (residues I-49) of the 13-kDa acidic rihosomal proteins from yeast 2. cerevisiae which are classified into PI-type proteins, Al and L44' (a), and P2-type proteins, A2 and L45 (b). Strengthened letters indicate hydrophobic amino acid residues and numbers in the parentheses indicate total numbers of amino acid residues in the proteins. Conventionally, the amino acid sequence is aligned in segments of seven amino acid residues (above) and the positions of the arrays containing the putative hydrophobic zippers (boxed) are marked on a helical wheel (below). characteristic 252)
domains
which
Out of
(11).
corresponds
to
the
in position
is
to be composed of
three
with
of
residues
Of particular of
interest
aliphatic
the
domain
residue of
domain of A0 is region
not
zipper
shown).
containing
in binding
raises
proteins
also
associate
with
Thus,
the
residues a typical
a possibility have
seventh
a leucine
that
helical
zipper
AO. 1320
from
in the if
except
possesses
the
appearance
the
whole
The secondary
1).
leucine
25 1).
position
LLLLAIIA,
which
(Fig.
the
results
second and third
A0 probably
than
carboxy-terminus
however,
zipper,
generally
205-
13-kDa
one another
which
(Fig.
of
to Chou and Fasman (12)
including
alanine
activity
finding
according
is,
every
225,
an alpha-helix
that
(data
at
(residues
of a segment of about
50% to
domain
leucine
analysis
containing
about
half
homologous
repeats
at position
structure this
the
residues
an elongated
constitutes
to
in this
amino acid
leucine
formation
relative
a similarity
a domain
amino-terminal
proteins found
them,
is
predicts for
residues
an atypical
leucine
zipper acidic
or a similar
proline
leucine
expected
13-kDa
the
to be lower
(9).
This
ribosomal structure
to
Vol.
174,
No.
3, 1991
BIOCHEMICALAND
COMMUNICATIONS
(a)
(b) Al
1>44' PI
Cc) A2
P2
Fiq.3. Conservation of the amino acid residues which comprise the hydrophobic zippers in yeast and human acidic ribosomal proteins; proteins (c). The amino acid PO- (a), PI- (b) and PZ-type residues comprising the hydrophobic zipper are boxed. Numbers indicate the positions of the amino acid residues. Ribosomes acidic
13-kDa
PI-type the
(Al
from
ribosomal and L44')
heterogeneity
whether
they
amino acid analyzed
by helical
of
is
proteins
zipper
the
on a putative
(Fig.
and L44',
are
residues
as the
leucine.
It
is
of
particular
interest
opposite
sides
of
a putative
alpha-helix
hydrophobic also
zipper.
Similarly,
shown to possess
putative
alpha-helix
the
total
the
positions
different
a bilateral (Fig.
amino acid of
between
proteins
must
proteins
because
be
the
residues residues
them. lower the
2a).
The PI-type
shown to have two
they
between comprising
contain 1321
refer
residues
besides
on the
"bilateral" A2 and L45,
due to
on a
(106
zippers
than
more alanine
are
the difference
A2 and L45
zippers
activity
to
because
zipper
the
or
zipper"
locate
proteins,
Probably
in binding
five
we like
forming
The hydrophobic
formers
have been
hydrophobic
2b).
their
halves
amino acid
P2-type
based on
structure,
"hydrophobic
that
into
To examine
(1).
Here,
hydrophobic
of
classified
containing
alpha-helix.
structure
composed of various
half
(9)
amino acid
are
species
(A2 ans L45)
amino-terminal
Al
four
or a similar
analysis
proteins,
hypothetical
which
amino-terminal
wheel
hydrophobic
residues
it
of
contain
(l-4)
and P2-type
sequences
arrays
the
proteins
have a leucine
ribosomal
to
S. cerevisiae -~-~
in the
acidic
seven
yeast
of
and
in IIO),
are P2-type
those
of
residues
PI-type and
Vol.
174,
No.
one of
3, 1991
the
proline.
zippers
According
amino-terminal to
containing most
of
region.
to
the
proline
these
it
of
side.
13-kDa
This
idea
that
the
were
released
salts
ribosomal
depending
on various
hydrophobic
zipper
leucine
zipper
exchange
may be more
with
So far, primary
those
has
or 3a).
phobic completely
substituted
in
the other
partly
hydrophobic a putative three-residue
hydrophobic with
yeast
idea
PI-type in
that
hand,
they
however,
conserved zipper
in of
zipper
human
amino
(Fig.3c). is
long
acid This
enough 1322
than
to
PO, the
whose amino
A0 are
bilateral
This the
are
almost further
hydrophobic of
may comprise
human
acids hydro-
finding
zipper
residues
acid
either
amino
ribosomes
zippers. yeast
A2 is
a bilateral
on each
may be interpreted in
a typical
and L44')
hydrophobic P2 which
yeast the
proteins
in
3b). via
13-kDa in
A0 homologue
(Al
associate
of
(14-16).
the
(Fig.
the
three
alpha-helix
Pl
ribosomes
of
hydrophobic
proteins
human
liver
Furthermore,
In
constituting
results
ribosome
zipper
similar
by
concentration
the
only
a side
previous
be weaker
(7).
will
make
copies
pool
the
to
rat
of
for
reported
those
conserved
supports On the
the
also
(14).
to
that
zipper
low
a mole
a cytosolic PO is
been
Similarly,
zipper
to
expected
in
a helical
as nine
convenient
protein
constituting
conserved (Fig.
free
human
structure
residues
is
in
the
conditions
which
are
of
in
as many
bound
growth
probable
by the
even
to
proteins
is
associating
proteins
50% ethanol
are
it
hydrophobic
indirectly
three
proteins region
proteins
ribosomal
the
(12),
the
to A0 but
ribosomal
acidic
that
the
bind
supported
with and
(13)
acidic
is
13-kDa
to
acidic
acids
of
acid,
and Fasman
Therefore,
location
COMMUNICATIONS
amino
including
amino
only
RESEARCH
ribosomal
alpha-helix residue.
not
Chou
acidic
hydrophobic
possible
network
of
13-kDa
in
BIOPHYSICAL
by a neutral
method
of
The bilateral
make
only
interrupted
be rich
the
AND
is
halves
predicted
the
BIOCHEMICAL
side
of
as
that
since
some
Vol.
174,
No.
structural
3, 1991
BIOCHEMICAL
changes
a different
site
amino-terminal
have of
To resolve
experiments
are
developed
being
BIOPHYSICAL
during
P2 protein,
sequence,
association.
AND
these
the
well
participate
problems,
COMMUNICATIONS
evolution.
possibly
may also
RESEARCH
in
further
Alternatively, conserved their analysis
and
undertaken. REFERENCES
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