ATP-dependent Hexameric Assembly of the
Heat Shock Protein Hsp101 Involves Multiple Interaction Domains and a
Functional C-proximal Nucleotide-binding Domain*
Daniel R.
Gallie
,
David
Fortner,
Jamy
Peng§, and
David
Puthoff¶
From the Department of Biochemistry, University of California,
Riverside, California 92521-0129
Members of the Hsp100 family of heat stress
proteins are present in species throughout the bacterial, plant, and
fungal kingdoms. Most Hsp100 proteins are composed of five domains that
include two nucleotide-binding domains required for their
ATP-dependent oligomerization. Mutations within the first
but not the second nucleotide-binding site disrupt self-assembly of
bacterial Hsp100, whereas the reverse is true for yeast Hsp104. We have
examined the functional requirements for oligomerization of plant
Hsp101 and have found that Hsp101 resembles Hsp104 in that it assembles into a hexameric complex in an ATP-dependent manner.
Self-assembly of Hsp101 involves at least three distinct interaction
domains located in the N-proximal domain and in the first and second
nucleotide-binding domains. The interaction domain in the second
nucleotide-binding domain included the Walker A motif, and mutations
within this element disrupted self-assembly of Hsp101. In contrast,
mutations affecting conserved residues of the Walker A motif within the first nucleotide-binding site did not affect self-assembly. No interaction between Hsp101 and Hsp104 was observed. These results suggest that plant Hsp101 self-assembly involves multiple
evolutionarily diverged interaction domains as well as an
evolutionarily conserved requirement for a functional C-proximal
nucleotide-binding site.
*
This work was supported by Grant NRICGP 00-35301-9086 from
the United States Department of Agriculture and Grant MCB-9816657 from
the National Science Foundation.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in accordance with 18 U.S.C. Section
1734 solely to indicate this fact.