Chaperone activity and homo- and hetero-oligomer formation of bacterial small heat shock proteins.
Rhizobia are the only bacteria known to induce a multitude of small heat shock proteins (sHsps) upon temperature upshift. The sHsps of Bradyrhizobium japonicum fall into two different classes, class A and class B. Here, we studied the chaperone activity and oligomeric features of two representative members of each class. The purified sHsps were efficient chaperones, as demonstrated by their ability to prevent thermally induced aggregation of citrate synthase in vitro. Homo-oligomer formation of all four sHsps was demonstrated by gel filtration and by two independent co-purification approaches. Mixed oligomers were readily observed between members of the same class, even when these proteins originated from different species such as Escherichia coli and B. japonicum. The chaperone activity of purified hetero-oligomers was indistinguishable from the activity of homo-oligomers. Heteromeric complexes were never obtained between class A and class B sHsps, indicating that hetero-oligomer formation is restricted to sHsps of the same class.
Studer
S
S
Institute of Microbiology, Eidgenössische Technische Hochschule, Schmelzbergstrasse 7, CH-8092 Zürich, Switzerland.
Narberhaus
F
F
D020369:Bradyrhizobium / Q000378:metabolism*; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002479:Inclusion Bodies / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism*; D011108:Polymers
D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; C097579:IbpB protein, E coli; D018832:Molecular Chaperones; D011108:Polymers