Crystal Structures of a T4-lysozyme Duplication-extension Mutant Demonstrate that the Highly Conserved beta-Sheet Region has Low Intrinsic Folding PropensitySagermann, M., Matthews, B.W.
(2002) J.Mol.Biol. 316: 931-940
- PubMed: 11884133
- DOI: 10.1006/jmbi.2001.5376
- Primary Citation of Related Structures:
- PubMed Abstract:
- Structural Characterization of an Engineered Tandem Repeat contrasts the Importance of Context and Sequence in Protein Folding
Sagermann, M.,Baase, W.A.,Matthews, B.W.
(1999) Proc.Natl.Acad.Sci.USA 96: 6078
- Structure of Bacteriophage T4 Lysozyme Refined at 1.7 A Resolution
Weaver, L.H.,Matthews, B.W.
(1987) J.Mol.Biol. 193: 189
Residues 24 to 35 of T4 lysozyme correspond to the second and third strands of a region of beta-sheet that is highly conserved in all known lysozyme and chitinase structures. To evaluate the intrinsic propensity of these amino acid residues to form a ...
Residues 24 to 35 of T4 lysozyme correspond to the second and third strands of a region of beta-sheet that is highly conserved in all known lysozyme and chitinase structures. To evaluate the intrinsic propensity of these amino acid residues to form a defined structure they were added at the C terminus of the native protein, together with a dipeptide linker. Two crystal structures of this active, mutant protein were obtained, to 1.9A and 2.3A resolution, respectively. Even though the crystal conditions are similar, the appended sequence adopts very different secondary structures. In one case it is weakly structured and appears to extend through the active-site cleft, perhaps in part adding an extra strand to the original beta-sheet. In the other crystal form the extension is largely alpha-helical. The formation of these alternative structures shows that the sequence does not have a strong intrinsic propensity to form a unique fold (either beta-sheet or otherwise). The results also suggest that structural conservation during evolution does not necessarily depend on sequence conservation or the conservation of folding propensity.
Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, 1229 University of Oregon, Eugene, OR 97403-1229, USA.