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

Summary: Interdependent Folding of the N- and C-Terminal Domains Defines the Cooperative
Folding of R-Lytic Protease
Erin L. Cunningham, and David A. Agard*,,,|
The Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, Graduate Group in Biophysics,
UniVersity of California at San Francisco, San Francisco, California 94143-2240
ReceiVed August 8, 2003; ReVised Manuscript ReceiVed September 18, 2003
ABSTRACT: R-Lytic protease (RLP) serves as an important model in achieving a quantitative and physical
understanding of protein folding reactions. Synthesized as a pro-protease, RLP belongs to an interesting
class of proteins that require pro regions to facilitate their proper folding. RLP's pro region (Pro) acts as
a potent folding catalyst for the protease, accelerating RLP folding to its native conformation nearly 1010-
fold. Structural and mutational studies suggested that Pro's considerable foldase activity is directed toward
structuring the RLP C-terminal domain (CRLP), a seemingly folding-impaired domain, which is believed
to contribute significantly to the high-energy folding and unfolding transition states of RLP. Pro-mediated
nucleation of RLP folding within CRLP was hypothesized to subsequently enable the RLP N-terminal
domain (NRLP) to dock and fold, completing the formation of native protease. In this paper, we find that
ternary folding reactions of Pro and noncovalent NRLP and CRLP domains are unaffected by the order
in which the components are added or by the relative concentrations of the RLP domains, indicating that
neither discrete CRLP structuring nor docking of the two RLP 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 NRLP and CRLP domains to form active protease. This cooperative and interdependent


Source: Agard, David - Department of Biochemistry and Biophysics, University of California at San Francisco


Collections: Biotechnology; Biology and Medicine