A pathway for conformational diversity in proteins mediated by intramolecular chaperones.
Conformational diversity within unique amino acid sequences is observed in diseases like scrapie and Alzheimer's disease. The molecular basis of such diversity is unknown. Similar phenomena occur in subtilisin, a serine protease homologous with eukaryotic pro-hormone convertases. The subtilisin propeptide functions as an intramolecular chaperone (IMC) that imparts steric information during folding but is not required for enzymatic activity. Point mutations within IMCs alter folding, resulting in structural conformers that specifically interact with their cognate IMCs in a process termed "protein memory." Here, we show a mechanism that mediates conformational diversity in subtilisin. During maturation, while the IMC is autocleaved and subsequently degraded by the active site of subtilisin, enzymatic properties of this site differ significantly before and after cleavage. Although subtilisin folded by Ile-48 --> Thr IMC (IMCI-48T) acquires an "altered" enzymatically active conformation (SubI-48T) significantly different from wild-type subtilisin (SubWT), both precursors undergo autocleavage at similar rates. IMC cleavage initiates conformational changes during which the IMC continues its chaperoning function subsequent to its cleavage from subtilisin. Structural imprinting resulting in conformational diversity originates during this reorganization stage and is a late folding event catalyzed by autocleavage of the IMC.
Shinde
U
U
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA.
Fu
X
X
Inouye
M
M
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000201:enzymology; D001665:Binding Sites; D004792:Enzyme Precursors / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D019791:Guanidine / Q000494:pharmacology; D007700:Kinetics; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics; D017354:Point Mutation; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D016415:Sequence Alignment; D013381:Subtilisins / Q000737:chemistry / Q000235:genetics; D013696:Temperature; D014508:Urea / Q000494:pharmacology
D004792:Enzyme Precursors; D018832:Molecular Chaperones; D010446:Peptide Fragments; D011994:Recombinant Proteins; C057107:prosubtilisin; D014508:Urea; D013381:Subtilisins; D019791:Guanidine