Single alanine and glycine insertions were introduced at 20 randomly selected positions in staphylococcal nuclease. The resulting changes in catalytic activity and in stability to guanidine hydrochloride denaturation indicate that the native state structure is frequently able to accommodate the extra residue without great difficulty, even insertions within secondary structural elements such as alpha helices and beta sheets. On average, an inserted residue reduces the free energy of denaturation (delta GH2O) by an amount roughly comparable to an alanine or glycine substitution for one of the residues flanking the site of insertion. Several positions outside of the enzyme active site were found where insertions, but not substitutions, lead to structural changes that modify catalytic activity and the circular dichroism spectrum. Amino acid insertions represent a virtually unexplored class of genetic mutation that may prove complementary to amino acid substitutions for engineering proteins with altered functional and structural properties. Study holds ProTherm entries: 2479, 2480, 2481, 2482, 2483, 2484, 2485, 2486, 2487, 2488, 2489, 2490, 2491, 2492, 2493, 2494, 2495, 2496, 2497, 2498, 2499, 2500, 2501, 2502, 2503, 2504, 2505 Extra Details:
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:19 p.m.
|Number of data points||79|
|Proteins||Thermonuclease ; Thermonuclease|
|Assays/Quantities/Protocols||Experimental Assay: activity ; Experimental Assay: m ; Experimental Assay: ddG|
|Libraries||Mutations for sequence ATSTKKLHKEPATLIKAIDGDTVKLMYKGQPMTFRLLLVDTPETKHPKKGVEKYGPEASAFTKKMVENAKKIEVEFDKGQRTDKYGRGLAYIYADGKMVNEALVRQGLAKVAYVYKPNNTHEQHLRKSEAQAKKEKLNIWSEDNADSGQ|