The in vivo function of the ribosome-associated Hsp70, Ssz1, does not require its putative peptide-binding domain

Heather Hundley, Helene Eisenman, William Walter, Tara Evans, Yuka Hotokezaka, Martin Wiedmann, Elizabeth Craig

Research output: Contribution to journalArticle

84 Citations (Scopus)

Abstract

Two proteins of the Hsp70 class (Ssb and Ssz1) and one of the J-type class (Zuo1) of molecular chaperones reside on the yeast ribosome, with Ssz1 forming a stable heterodimer with Zuo1. We designed experiments to address the roles of these two distantly related ribosome-associated Hsp70s and their functional relationship to Zuo1. Strains lacking all three proteins have the same phenotype as those lacking only one, suggesting that these chaperones all function in the same pathway. The Hsp70 Ssb, whose peptide-binding domain is essential for its in vivo function, can be crosslinked to nascent chains on ribosomes that are as short as 54 amino acids, suggesting that Ssb interacts with nascent chains that extend only a short distance beyond the tunnel of the ribosome. A ssz1 mutant protein lacking its putative peptide-binding domain allows normal growth. Thus, binding of unfolded protein substrates in a manner similar to that of typical Hsp70s is not critical for Ssz1's in vivo function. The three chaperones are present in cells in approximately equimolar amounts compared with ribosomes. The level of Ssb can be reduced only a few-fold before growth is affected. However, a 50- to 100-fold reduction of Ssz1 and Zuo1 levels does not have a substantial effect on cell growth. On the basis of these results, we propose that Ssbs function as the major Hsp70 chaperone for nascent chains on the ribosome, and that Ssz1 has evolved to perform a nonclassical function, perhaps modulating Zuo1's ability to function as a J-type chaperone partner of Ssb.

Original languageEnglish (US)
Pages (from-to)4203-4208
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume99
Issue number7
DOIs
StatePublished - Apr 2 2002
Externally publishedYes

Fingerprint

Ribosomes
Growth
Molecular Chaperones
Mutant Proteins
Protein Domains
Carrier Proteins
Proteins
Yeasts
Phenotype
Amino Acids

ASJC Scopus subject areas

  • Genetics
  • General

Cite this

The in vivo function of the ribosome-associated Hsp70, Ssz1, does not require its putative peptide-binding domain. / Hundley, Heather; Eisenman, Helene; Walter, William; Evans, Tara; Hotokezaka, Yuka; Wiedmann, Martin; Craig, Elizabeth.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 99, No. 7, 02.04.2002, p. 4203-4208.

Research output: Contribution to journalArticle

Hundley, Heather ; Eisenman, Helene ; Walter, William ; Evans, Tara ; Hotokezaka, Yuka ; Wiedmann, Martin ; Craig, Elizabeth. / The in vivo function of the ribosome-associated Hsp70, Ssz1, does not require its putative peptide-binding domain. In: Proceedings of the National Academy of Sciences of the United States of America. 2002 ; Vol. 99, No. 7. pp. 4203-4208.
@article{4802a0ec31014637bb359cbe76113242,
title = "The in vivo function of the ribosome-associated Hsp70, Ssz1, does not require its putative peptide-binding domain",
abstract = "Two proteins of the Hsp70 class (Ssb and Ssz1) and one of the J-type class (Zuo1) of molecular chaperones reside on the yeast ribosome, with Ssz1 forming a stable heterodimer with Zuo1. We designed experiments to address the roles of these two distantly related ribosome-associated Hsp70s and their functional relationship to Zuo1. Strains lacking all three proteins have the same phenotype as those lacking only one, suggesting that these chaperones all function in the same pathway. The Hsp70 Ssb, whose peptide-binding domain is essential for its in vivo function, can be crosslinked to nascent chains on ribosomes that are as short as 54 amino acids, suggesting that Ssb interacts with nascent chains that extend only a short distance beyond the tunnel of the ribosome. A ssz1 mutant protein lacking its putative peptide-binding domain allows normal growth. Thus, binding of unfolded protein substrates in a manner similar to that of typical Hsp70s is not critical for Ssz1's in vivo function. The three chaperones are present in cells in approximately equimolar amounts compared with ribosomes. The level of Ssb can be reduced only a few-fold before growth is affected. However, a 50- to 100-fold reduction of Ssz1 and Zuo1 levels does not have a substantial effect on cell growth. On the basis of these results, we propose that Ssbs function as the major Hsp70 chaperone for nascent chains on the ribosome, and that Ssz1 has evolved to perform a nonclassical function, perhaps modulating Zuo1's ability to function as a J-type chaperone partner of Ssb.",
author = "Heather Hundley and Helene Eisenman and William Walter and Tara Evans and Yuka Hotokezaka and Martin Wiedmann and Elizabeth Craig",
year = "2002",
month = "4",
day = "2",
doi = "10.1073/pnas.062048399",
language = "English (US)",
volume = "99",
pages = "4203--4208",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
issn = "0027-8424",
number = "7",

}

TY - JOUR

T1 - The in vivo function of the ribosome-associated Hsp70, Ssz1, does not require its putative peptide-binding domain

AU - Hundley, Heather

AU - Eisenman, Helene

AU - Walter, William

AU - Evans, Tara

AU - Hotokezaka, Yuka

AU - Wiedmann, Martin

AU - Craig, Elizabeth

PY - 2002/4/2

Y1 - 2002/4/2

N2 - Two proteins of the Hsp70 class (Ssb and Ssz1) and one of the J-type class (Zuo1) of molecular chaperones reside on the yeast ribosome, with Ssz1 forming a stable heterodimer with Zuo1. We designed experiments to address the roles of these two distantly related ribosome-associated Hsp70s and their functional relationship to Zuo1. Strains lacking all three proteins have the same phenotype as those lacking only one, suggesting that these chaperones all function in the same pathway. The Hsp70 Ssb, whose peptide-binding domain is essential for its in vivo function, can be crosslinked to nascent chains on ribosomes that are as short as 54 amino acids, suggesting that Ssb interacts with nascent chains that extend only a short distance beyond the tunnel of the ribosome. A ssz1 mutant protein lacking its putative peptide-binding domain allows normal growth. Thus, binding of unfolded protein substrates in a manner similar to that of typical Hsp70s is not critical for Ssz1's in vivo function. The three chaperones are present in cells in approximately equimolar amounts compared with ribosomes. The level of Ssb can be reduced only a few-fold before growth is affected. However, a 50- to 100-fold reduction of Ssz1 and Zuo1 levels does not have a substantial effect on cell growth. On the basis of these results, we propose that Ssbs function as the major Hsp70 chaperone for nascent chains on the ribosome, and that Ssz1 has evolved to perform a nonclassical function, perhaps modulating Zuo1's ability to function as a J-type chaperone partner of Ssb.

AB - Two proteins of the Hsp70 class (Ssb and Ssz1) and one of the J-type class (Zuo1) of molecular chaperones reside on the yeast ribosome, with Ssz1 forming a stable heterodimer with Zuo1. We designed experiments to address the roles of these two distantly related ribosome-associated Hsp70s and their functional relationship to Zuo1. Strains lacking all three proteins have the same phenotype as those lacking only one, suggesting that these chaperones all function in the same pathway. The Hsp70 Ssb, whose peptide-binding domain is essential for its in vivo function, can be crosslinked to nascent chains on ribosomes that are as short as 54 amino acids, suggesting that Ssb interacts with nascent chains that extend only a short distance beyond the tunnel of the ribosome. A ssz1 mutant protein lacking its putative peptide-binding domain allows normal growth. Thus, binding of unfolded protein substrates in a manner similar to that of typical Hsp70s is not critical for Ssz1's in vivo function. The three chaperones are present in cells in approximately equimolar amounts compared with ribosomes. The level of Ssb can be reduced only a few-fold before growth is affected. However, a 50- to 100-fold reduction of Ssz1 and Zuo1 levels does not have a substantial effect on cell growth. On the basis of these results, we propose that Ssbs function as the major Hsp70 chaperone for nascent chains on the ribosome, and that Ssz1 has evolved to perform a nonclassical function, perhaps modulating Zuo1's ability to function as a J-type chaperone partner of Ssb.

UR - http://www.scopus.com/inward/record.url?scp=0037007008&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0037007008&partnerID=8YFLogxK

U2 - 10.1073/pnas.062048399

DO - 10.1073/pnas.062048399

M3 - Article

VL - 99

SP - 4203

EP - 4208

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

SN - 0027-8424

IS - 7

ER -