Two mutants of phage T4 lysozyme were prepared and characterized. One mutation substituted a tyrosine residue for tryptophan at position 138. The other substituted tyrosines at all three tryptophan positions of the wild type molecule (126, 138, 158). Comparative studies of the physical properties (absorption, fluorescence, circular dichroism) of the three enzymes were performed as a function of pH. Also, the proteins were reversibly melted as a function of pH. Since the unfolding reaction appeared to be a two-state process for all these proteins, the data were analyzed by the van 't Hoff procedure. The changes in stability and activity produced by substitution of Trp 138 were especially significant. The other substitutions were neutral. See the end of the paper for a summary of conclusions. In the appendix the appropriate thermodynamic relations are developed for a constant deltaCp transition. Study holds ProTherm entries: 1215, 1216, 1217, 1218, 1219, 13612, 13613, 13614 Extra Details: bacteriophage T4 lysozyme; tyrosine; tryptophan;,thermal stability
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:16 p.m.
|Number of data points||35|
|Proteins||Endolysin ; Endolysin|
|Assays/Quantities/Protocols||Experimental Assay: ddG pH:2.5 ; Experimental Assay: ddG pH:2.2 ; Experimental Assay: activity pH:2.5 ; Experimental Assay: Tm pH:2.5 ; Experimental Assay: dHvH pH:2.5 ; Experimental Assay: activity pH:2.2 ; Experimental Assay: Tm pH:2.2 ; Experimental Assay: dHvH pH:2.2 ; Derived Quantity: dTm pH:2.5 ; Derived Quantity: dTm pH:2.2|
|Libraries||Mutations for sequence MNIFEMLRIDEGLRLKIYKDTEGYYTIGIGHLLTKSPSLNAAKSELDKAIGRNCNGVITKDEAEKLFNQDVDAAVRGILRNAKLKPVYDSLDAVRRCALINMVFQMGETGVAGFTNSLRMLQQKRWDEAAVNLAKSRWYNQTPNRAKRVITTFRTGTWDAYKNL|