12] Chaperonin 6014 and co-chaperonin 107 from Chromatium vinosum

Abstract

Publisher Summary Chaperonins are a specialized class of proteins that promote assembly, disassembly, or translocation of other proteins in an ATP-dependent reaction. The heat shock proteins, chaperonin 60 (Cpn60) and chaperonin 10 (Cpnl0) from Escherichia coli, previously designated as GroEL and GroES, respectively, are classic representatives of the molecular chaperone family. Chaperonins 60 and 10 are ubiquitous in nature as similar proteins have been identified in a wide variety of prokaryotes and organelles, such as the peroxisome, chloroplast, mitochondrion, Golgi apparatus, and endoplasmic reticulum. In regard to their native structure, Cpn60 generally comprises 14 identical 60-kDa subunits arranged in a double-layered structure with a seven-fold symmetry. However, Cpnl0 is a seven-subunit homo-oligomer with a subunit molecular mass of 10 kDa. The evidence that Cpn60 and Cpnl0 interact functionally with each other has been strongly supported by both genetic and biochemical approaches. Cpn60 and Cpnl0 homologs are identified in Chromatium vinosum, an oxygenic photosynthetic purple sulfur bacterium. The data indicate that Cpn60 and Cpnl0 from C. vinosum resemble, structurally and functionally, their counterparts from E. coli. The presence of Cpn60 and ribulose-bisphosphate carboxylase/oxygenase (Rubisco) in the crude extracts of C. vinosum, grown photoheterotrophically, may be quantified by enzyme-linked immunosorbent assay (ELISA), using the “sandwich method” according to established protocols.