Systematic mutation of bacteriophage T4 lysozyme.

摘要: Abstract Amber mutations were introduced into every codon (except the initiating AUG) of bacteriophage T4 lysozyme gene. The amber alleles a P22 hybrid, called e416, in which normal gene is replaced by its homologue, and consequently depends upon for ability to form plaque. resulting mutants tested plaque formation on suppressor strains Salmonella typhimurium. Experiments with other hybrid phages engineered produce different amounts wild-type have shown that, score as deleterious, mutation must reduce activity less than 3% that produced e416. Plating collection covering 163 164 codons lysozyme, 13 each insert amino acid residue response codon, tests effects multiple single substitutions at position protein first). Of 2015 328 found be sufficiently deleterious inhibit formation. More half (55%) positions tolerated all examined. Among (N-terminal) fragments, only those 161 or more residues are active. many interpretable light known structure lysozyme. Residues molecule refractory replacements generally solvent-inaccessible side-chains; catalytic Glu11 Asp20 notable exceptions. Especially sensitive sites include involved buried salt bridges near site (Asp10, Arg145 Arg148) few others may critical structural roles (Gly30, Trp138 Tyr161).