Assembly chaperones: a perspective

Abstract

The historical origins and current interpretation of the molecular chaperone concept are presented, with the emphasis on the distinction between folding chaperones and assembly chaperones. Definitions of some basic terms in this field are offered and misconceptions pointed out. Two examples of assembly chaperone are discussed in more detail: the role of numerous histone chaperones in fundamental nuclear processes and the co-operation of assembly chaperones with folding chaperones in the production of the world's most important enzyme.

Structure of GPN-Loop GTPase Npa3 and Implications for RNA Polymerase II Assembly

“…Therefore, it is likely that the newly observed hydrophobic pocket of Npa3 binds hydrophobic peptides in the cellular context. We therefore considered that the hydrophobic pocket naturally binds to hydrophobic protein regions as described for molecular chaperones that prevent misassembly and aggregation of multisubunit complexes (1,2). Indeed, modeling showed that hydrophobic peptides may be accommodated in the pocket in an extended conformation.…”

“…Many macromolecular complexes have been shown to require assembly chaperones for their biogenesis (2), including the nucleosome (36,37), RuBisCO (38), the proteasome (39), spliceosomal snRNPs (40), and the ribosome (41). In contrast, biogenesis of the 12-subunit Pol II complex remains poorly understood.…”

“…Thermal aggregation of CS was essentially carried out as described previously (29) 2 ) in the absence of nucleotides or preheated (43°C) buffer C containing 100 mM NaCl (pH 7.5) (43°C) in the presence of 1 mM GMPPCP, GTP, or GDP, and various amounts of Npa3 were added. For experiments where GMPPCP or GDP was added, Npa3 samples were incubated with the respective nucleotide overnight at 4°C for nucleotide exchange.…”

“…rotein folding was studied mainly for individual proteins (1), but most eukaryotic proteins form complexes, and their assembly is often poorly understood (2). A prominent eukaryotic protein complex is RNA polymerase II (Pol II), a 12-subunit, 520-kDa enzyme that carries out transcription of protein-encoding genes.…”

Structure and mechanism of the Rubisco-assembly chaperone Raf1

“…The biogenesis of hexadecameric Rubisco has emerged as a paradigm of assisted assembly 30,31 . Here we analyzed the structure Our results demonstrate that the dimeric Raf1 functions downstream of RbcL-subunit folding by the GroEL-ES chaperonin system.…”