On exposure to mildly acidic conditions, apomyoglobin forms a partially folded intermediate, I. The A, B, G, and H helices are significantly structured in this equilibrium intermediate, whereas the remainder of the protein is largely unfolded. We report here the effects of mutations at helix pairing sites on the stability of I in three classes of mutants that: (i) truncate hydrophobic side chains in native helix packing sites, (ii) truncate hydrophobic side chains not involved in interhelical contacts, and (iii) extend hydrophobic side chains at residues not involved in interhelical contacts. Class I mutants significantly decrease the stability and cooperativity of folding of the intermediate. Class II and III mutants show smaller effects on stability and have little effect on cooperativity. Qualitatively similar results to those found in I were obtained for all three classes of mutants in native myoglobin (N), demonstrating that hydrophobic burial is fairly specific to native helix packing sites in I as well as in N. These results suggest that hydrophobic burial along native-like interhelical contacts is important for the formation of the cooperatively folded intermediate. Study holds ProTherm entries: 6503, 6504, 6505, 6506, 6507, 6508, 6509, 6510, 6511, 6512, 6513, 6514, 6515, 6516, 6517, 6518, 6519, 6520, 6521, 6522, 6523, 6524, 6525, 6526, 6527, 6528, 6529, 6530, 6531, 6532, 6533, 6534, 6535, 6536, 6537, 6538, 6539, 6540, 6541, 6542, 6543, 6544, 6545, 6546 Extra Details: partially folded intermediate state partially folded intermediate; helix packing sites;,hydrophobic side chains; helix pairing; hydrophobic burial
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:32 p.m.
|Number of data points||84|
|Proteins||Myoglobin ; Myoglobin|
|Assays/Quantities/Protocols||Experimental Assay: ddG_H2O pH:5.0, details:Additives NaCN (0.5 mM),, temp:25.0 C, buffers:acetate: 10 mM ; Experimental Assay: Cm pH:5.0, details:Additives NaCN (0.5 mM),, temp:25.0 C, buffers:acetate: 10 mM ; Experimental Assay: ddG_H2O pH:5.0, details:Additives NaCN (0.5 mM),, temp:25.0 C, buffers:acetate: 10 mM ; Experimental Assay: Cm pH:5.0, details:Additives NaCN (0.5 mM),, temp:25.0 C, buffers:acetate: 10 mM ; Experimental Assay: ddG_H2O pH:4.2, buffers:citrate: 4 mM, details:Additives , temp:4.0 C ; Experimental Assay: Cm pH:4.2, buffers:citrate: 4 mM, details:Additives , temp:4.0 C ; Experimental Assay: ddG_H2O pH:4.2, details:Additives , buffers:citrate: 4 mM, temp:4.0 C ; Experimental Assay: Cm pH:4.2, details:Additives , buffers:citrate: 4 mM, temp:4.0 C|
|Libraries||Mutations for sequence VLSEGEWQLVLHVWAKVEADVAGHGQDILIRLFKSHPETLEKFDRFKHLKTEAEMKASEDLKKHGVTVLTALGAILKKKGHHEAELKPLAQSHATKHKIPIKYLEFISEAIIHVLHSRHPGDFGADAQGAMNKALELFRKDIAAKYKELGYQG|
|Percent Identity||Matching Chains||Protein||Accession||Entry Name|