Interdependent Folding of the N- and C-Terminal Domains Defines the Cooperative Folding of α-Lytic Protease

Publisher Website
Google Scholar
Abstract
α-Lytic protease (αLP) serves as an important model in achieving a quantitative and physical understanding of protein folding reactions. Synthesized as a pro-protease, αLP belongs to an interesting class of proteins that require pro regions to facilitate their proper folding. αLP's pro region (Pro) acts as a potent folding catalyst for the protease, accelerating αLP folding to its native conformation nearly 1010-fold. Structural and mutational studies suggested that Pro's considerable foldase activity is directed toward structuring the αLP C-terminal domain (CαLP), a seemingly folding-impaired domain, which is believed to contribute significantly to the high-energy folding and unfolding transition states of αLP. Pro-mediated nucleation of αLP folding within CαLP was hypothesized to subsequently enable the αLP N-terminal domain (NαLP) to dock and fold, completing the formation of native protease. In this paper, we find that ternary folding reactions of Pro and noncovalent NαLP and CαLP domains are unaffected by the order in which the components are added or by the relative concentrations of the αLP domains, indicating that neither discrete CαLP structuring nor docking of the two αLP domains is involved in the folding transition state. Instead, the rate-limiting step of these folding reactions appears to be a slow and concerted rearrangement of the NαLP and CαLP domains to form active protease. This cooperative and interdependent folding of both protease domains defines the large αLP folding barrier and is an apparent extension of the highly cooperative αLP unfolding transition that imparts the protease with remarkable kinetic stability and functional longevity.

This publication has 3 references indexed in Scilit: