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Core mutants of the immunoglobulin binding domain of streptococcal protein G: Stability and structural integrity
Author(s) -
Gronenborn Angela M.,
Frank M.Kirsten,
Clore G.Marius
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(96)01262-8
Subject(s) - heteronuclear molecule , mutant , chemistry , heteronuclear single quantum coherence spectroscopy , amino acid , nuclear magnetic resonance spectroscopy , crystallography , residue (chemistry) , protein structure , beta sheet , two dimensional nuclear magnetic resonance spectroscopy , stereochemistry , biochemistry , biophysics , biology , gene
A library of core mutants of the GB1 domain of streptococcal protein G was created, and the structure and stability of selected members was assessed by 1 H‐ 15 N heteronuclear correlation NMR spectroscopy and fluorescence. All mutants comprised changes in β‐sheet residues, with sidechains at positions 5 (Leu), 7 (Leu), 52 (Phe) and 54 (Val) forming the β‐sheet side of the sheet‐helix core interface. A solvent exposed position Ile‐6 was chosen as a control. Randomization of bases at codon positions 1 and 3 with thymine at position 2 introduces five possible hydrophobic amino acids, namely Leu, Val, Ile, Phe, and Met. The distribution of encoded amino acids at all five positions is approximately as expected theoretically and indicates that no major bias was introduced towards particular residues. The overall structural integrity of several mutants, as assessed by NMR, ranges from very close to wild type to fully unfolded. Interestingly, the stability of the mutants is not strictly correlated with the number of changes or residue volume.