Structural studies of mutants of T4 lysozyme that alter hydrophobic stabilization.

摘要: Abstract Multiple replacements at amino acid position 3 of bacteriophage T4 lysozyme have shown that the conformational stability protein is directly governed by hydrophobicity residue substituted (Matsumura, M., Becktel, W. J., and Matthews, B. (1988) Nature 334, 406-410). Of 13 mutant lysozymes made site-directed mutagenesis, two variants, one with valine (I3V) other tyrosine (I3Y), were crystallized their structures solved. In this report we describe crystal these variants 1.7 A resolution. While structure I3V essentially same as wild-type lysozyme, I3Y has substantial changes in its structure. The most significant are side chain not accommodated within interior amino-terminal polypeptide (residues 1-9) moves 0.6-1.1 relative to Using coordinates based on available structures, solvent accessible surface area well adjacent 9 residues folded form calculated. free energy stabilization transfer from a fully extended was found correlate determined thermodynamic analysis. enhanced thermostability variant Ile-3----Leu, can also be rationalized surface-area calculations model-built Noncrystallization appears due disruption intermolecular contacts crystal. Ile-3----Val closely isomorphous maintains contacts. Ile-3----Tyr variant, however, new set which direct protein-protein hydrogen bonds replaced protein-water-protein novel bond involving phenolic hydroxyl tyrosine.