Putative interhelix ion pairs involved in the stability of myoglobin.


An earlier theoretical study predicted that specific ion pair interactions between neighboring helices should be important in stabilizing myoglobin. To measure these interactions in sperm whale myoglobin, single mutations were made to disrupt them. To obtain reliable DeltaG values, conditions were found in which the urea induced unfolding of holomyoglobin is reversible and two-state. The cyanomet form of myoglobin satisfies this condition at pH 5, 25 degrees C. The unfolding curves monitored by far-UV CD and Soret absorbance are superimposable and reversible. None of the putative ion pairs studied here makes a large contribution to the stability of native myoglobin. The protein stability does decrease somewhat between 0 and 0.1 M NaCl, however, indicating that electrostatic interactions contribute favorably to myoglobin stability at pH 5.0. A previous mutational study indicated that the net positive charge of the A[B]GH subdomain of myoglobin is an important factor affecting the stability of the pH 4 folding intermediate and potential ion pairs within the subdomain do not contribute significantly to its stability. One of the assumptions made in that study is tested here: replacement of either positively or negatively charged residues outside the A[B]GH subdomain has no significant effect on the stability of the pH 4 molten globule. Study holds ProTherm entries: 5899, 5900, 5901, 5902, 5903, 5904, 5905, 5906, 5907, 5908, 5909, 5910, 5911, 5912 Extra Details: KCN(0.5 mM) was added in the experiment ion pair interaction; unfolding curve; electrostatic; stability

Submission Details

ID: CtrtAbrd

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:31 p.m.

Version: 1

Publication Details
Ramos CH;Kay MS;Baldwin RL,Biochemistry (1999) Putative interhelix ion pairs involved in the stability of myoglobin. PMID:10423259
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
90.1 Myoglobin P02182 MYG_ZIPCA
90.1 Myoglobin Q0KIY0 MYG_MESST
90.1 Myoglobin P02183 MYG_MESCA
90.3 Myoglobin P02180 MYG_BALPH
90.9 Myoglobin P02179 MYG_BALAC
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
92.1 Myoglobin P02174 MYG_GLOME
91.4 Myoglobin P02181 MYG_INIGE
92.2 Myoglobin P02178 MYG_MEGNO
91.4 Myoglobin Q0KIY3 MYG_PENEL
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