2o79

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spinqualitylabelsall models 2o79, resolution 1.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

T4 lysozyme with C-terminal extension

Overview

Small proteins are generally observed to fold in an apparent two-state, manner. Recently, however, more sensitive techniques have demonstrated, that even seemingly single-domain proteins are actually made up of smaller, subdomains. T4 lysozyme is one such protein. We explored the relative, autonomy of its two individual subdomains and their contribution to the, overall stability of T4 lysozyme by examining a circular permutation, (CP13*) that relocates the N-terminal A-helix, creating subdomains that, are contiguous in sequence. By determining the high-resolution structure, of CP13* and characterizing its energy landscape using native state, hydrogen exchange (NSHX), we show that connectivity between the subdomains, is an important determinant of the energetic cooperativity but not, structural integrity of the protein. The circular permutation results in a, protein more easily able to populate a partially unfolded form in which, the C-terminal subdomain is folded and the N-terminal subdomain is, unfolded. We also created a fragment model of this intermediate and, demonstrate using X-ray crystallography that its structure is identical to, the corresponding residues in the full-length protein with the exception, of a small network of hydrophobic interactions. In sum, we conclude that, the C-terminal subdomain dominates the energetics of T4 lysozyme folding, and the A-helix serves an important role in coupling the two subdomains.

About this Structure

2O79 is a Single protein structure of sequence from Bacteriophage t4 with , and as ligands. Active as Lysozyme, with EC number 3.2.1.17 Full crystallographic information is available from OCA.

Reference

Exploring subdomain cooperativity in T4 lysozyme I: Structural and energetic studies of a circular permutant and protein fragment., Cellitti J, Llinas M, Echols N, Shank EA, Gillespie B, Kwon E, Crowder SM, Dahlquist FW, Alber T, Marqusee S, Protein Sci. 2007 Mar 30;. PMID:17400926

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