Energetics of side chain packing in staphylococcal nuclease assessed by exchange of valines, isoleucines, and leucines.


To examine the importance of side chain packing to protein stability, each of the 11 leucines in staphylococcal nuclease was substituted with isoleucine and valine. The nine valines were substituted with leucine and isoleucine, while the five isoleucines, previously substituted with valine, were substituted with leucine and methionine. These substitutions conserve the hydrophobic character of these side chains but alter side chain geometry and, in some cases, size. In addition, eight threonine residues, previously substituted with valine, were substituted with isoleucine to test the importance of packing at sites normally not occupied by a hydrophobic residue. The stabilities of these 58 mutant proteins were measured by guanidine hydrochloride denaturation. To the best of our knowledge, this is the largest library of single packing mutants yet characterized. As expected, repacking stability effects are tied to the degree of side chain burial. The average energetic cost of moving a single buried methyl group was 0.9 kcal/mol, albeit with a standard deviation of 0.8 kcal/mol. This average is actually slightly greater than the value of 0.7-0.8 kcal/mol estimated for the hydrophobic transfer energy of a methylene from octanol to water. These results appear to indicate that van der Waals interactions gained from optimal packing are at least as important in stabilizing the native state of proteins as hydrophobic transfer effects. Study holds ProTherm entries: 12585, 12586, 12587, 12588, 12589, 12590, 12591, 12592, 12593, 12594, 12595, 12596, 12597, 12598, 12599, 12600, 12601, 12602, 12603, 12604, 12605, 12606, 12607, 12608, 12609, 12610, 12611, 12612, 12613, 12614, 12615, 12616, 12617, 12618, 12619, 12620, 12621, 12622, 12623, 12624, 12625, 12626, 12627, 12628, 12629, 12630, 12631, 12632, 12633, 12634, 12635, 12636, 12637, 12638, 12639, 12640, 12641, 12642, 12643 Extra Details: side chain packing; hydrophobic character; repacking stability effects;,buried methyl group; hydrophobic transfer effects

Submission Details


Submitter: Connie Wang

Submission Date: April 24, 2018, 8:43 p.m.

Version: 1

Publication Details
Holder JB;Bennett AF;Chen J;Spencer DS;Byrne MP;Stites WE,Biochemistry (2001) Energetics of side chain packing in staphylococcal nuclease assessed by exchange of valines, isoleucines, and leucines. PMID:11705391
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Thermonuclease P00644 NUC_STAAU
99.3 Thermonuclease Q5HHM4 NUC_STAAC
99.1 Thermonuclease Q99VJ0 NUC_STAAM
99.1 Thermonuclease Q7A6P2 NUC_STAAN
99.3 Thermonuclease Q6GB41 NUC_STAAS
99.3 Thermonuclease Q8NXI6 NUC_STAAW
99.3 Thermonuclease Q6GIK1 NUC_STAAR