Folding pathway mediated by an intramolecular chaperone: The structural and functional characterization of the aqualysin I propeptide

Cynthia Marie-Claire, Yukihiro Yabuta, Kyoko Suefuji, Hiroshi Matsuzawa, Ujwal Shinde

Research output: Contribution to journalArticle

42 Scopus citations


Aqualysin I, a thermostable homologue of subtilisin, requires its propeptide (ProA) to function as an intramolecular chaperone (IMC). To decipher the mechanisms through which propeptides can initiate protein folding, we characterized ProA in terms of its sequence, structure and function. Our results show that, in contrast to ProS (propeptide of subtilisin), ProA can fold spontaneously, reversibly and cooperatively into a stable monomeric α-β conformation, even when isolated from its cognate protease-domain. ProA displays an indiscernible amount of tertiary structure with a considerable solvent-accessible hydrophobic surface, but is not a classical molten-globule folding intermediate. Moreover, despite showing only 21% sequence identity with ProS, ProA can not only inhibit enzymatic activity with a magnitude tenfold greater than ProS, but can also chaperone subtilisin folding, albeit with a lower efficiency. The structure of ProA complexed with subtilisin is different from that of isolated ProA. Hence, additional interactions seem necessary to induce ProA into a compact structure. Our results also suggest that: (a) propeptides that are potent inhibitors are not necessarily better IMCs; (b) propeptides within the subtilase family appear polymorphic and; (c) the intrinsic instability within propeptides may be necessary for rapid activation of the cognate protein.

Original languageEnglish (US)
Pages (from-to)151-165
Number of pages15
JournalJournal of molecular biology
Issue number1
StatePublished - Jan 5 2001



  • Aqualysin I
  • Propeptides
  • Protein folding
  • Serine proteases
  • Subtilisin

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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