Effects of alanine substitutions in alpha-helices of sperm whale myoglobin on protein stability.


The peptide backbones in folded native proteins contain distinctive secondary structures, alpha-helices, beta-sheets, and turns, with significant frequency. One question that arises in folding is how the stability of this secondary structure relates to that of the protein as a whole. To address this question, we substituted the alpha-helix-stabilizing alanine side chain at 16 selected sites in the sequence of sperm whale myoglobin, 12 at helical sites on the surface of the protein, and 4 at obviously internal sites. Substitution of alanine for bulky side chains at internal sites destabilizes the protein, as expected if packing interactions are disrupted. Alanine substitutions do not uniformly stabilize the protein, either in capping positions near the ends of helices or at mid-helical sites near the surface of myoglobin. When corrected for the extent of exposure of each side chain replaced by alanine at a mid-helix position, alanine replacement still has no clear effect in stabilizing the native structure. Thus linkage between the stabilization of secondary structure and tertiary structure in myoglobin cannot be demonstrated, probably because of the relatively small free energy differences between side chains in stabilizing isolated helix. By contrast, about 80% of the variance in free energy observed can be accounted for by the loss in buried surface area of the native residue substituted by alanine. The differential free energy of helix stabilization does not account for any additional variation. Study holds ProTherm entries: 527, 528, 529, 530, 531, 532, 533, 534, 535, 536, 537, 538, 539, 540, 541, 542, 13328, 13329, 13330, 13331, 13332, 13333, 13334, 13335, 13336, 13337, 13338, 13339, 13340, 13341, 13342 Extra Details: alpha-helix; helix capping; protein folding; secondary,structure; tertiary structure

Submission Details

ID: ayr2bwzS3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:15 p.m.

Version: 1

Publication Details
Pinker RJ;Lin L;Rose GD;Kallenbach NR,Protein Sci. (1993) Effects of alanine substitutions in alpha-helices of sperm whale myoglobin on protein stability. PMID:8358293
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 PDB Entries

Structure ID Release Date Resolution Structure Title
6BMG 2017-11-14T00:00:00+0000 1.88 Structure of Recombinant Dwarf Sperm Whale Myoglobin (Oxy)
5YCI 2017-09-07T00:00:00+0000 1.97 Ancestral myoglobin aMbWb' of Basilosaurus relative (polyphyly)
5YCJ 2017-09-07T00:00:00+0000 1.58 Ancestral myoglobin aMbWb' of Basilosaurus relative (polyphyly) imidazole-ligand
101M 1997-12-13T00:00:00+0000 2.07 SPERM WHALE MYOGLOBIN F46V N-BUTYL ISOCYANIDE AT PH 9.0
102M 1997-12-15T00:00:00+0000 1.84 SPERM WHALE MYOGLOBIN H64A AQUOMET AT PH 9.0
103M 1997-12-16T00:00:00+0000 2.07 SPERM WHALE MYOGLOBIN H64A N-BUTYL ISOCYANIDE AT PH 9.0
104M 1997-12-18T00:00:00+0000 1.71 SPERM WHALE MYOGLOBIN N-BUTYL ISOCYANIDE AT PH 7.0
105M 1997-12-18T00:00:00+0000 2.02 SPERM WHALE MYOGLOBIN N-BUTYL ISOCYANIDE AT PH 9.0
106M 1997-12-21T00:00:00+0000 1.99 SPERM WHALE MYOGLOBIN V68F ETHYL ISOCYANIDE AT PH 9.0
107M 1997-12-22T00:00:00+0000 2.09 SPERM WHALE MYOGLOBIN V68F N-BUTYL ISOCYANIDE AT PH 9.0

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
90.3 Myoglobin P02180 MYG_BALPH
90.8 Myoglobin P68278 MYG_PHOPH
90.8 Myoglobin P68277 MYG_PHODA
90.8 Myoglobin P68279 MYG_TURTR
90.8 Myoglobin P68276 MYG_DELDE
90.8 Myoglobin Q0KIY7 MYG1_STEAT
91.4 Myoglobin P02173 MYG_ORCOR
90.9 Myoglobin P02179 MYG_BALAC
92.1 Myoglobin P02174 MYG_GLOME
91.4 Myoglobin P02181 MYG_INIGE
91.4 Myoglobin Q0KIY3 MYG_PENEL
92.2 Myoglobin P02178 MYG_MEGNO
92.9 Myoglobin P02177 MYG_ESCRO
92.9 Myoglobin Q0KIY2 MYG_BALED
92.9 Myoglobin Q0KIY1 MYG_BALBO
96.8 Myoglobin P02184 MYG_KOGSI
96.8 Myoglobin Q0KIY5 MYG_KOGBR
100.0 Myoglobin P02185 MYG_PHYMC
90.1 Myoglobin P02182 MYG_ZIPCA
90.1 Myoglobin Q0KIY0 MYG_MESST
90.1 Myoglobin P02183 MYG_MESCA