Using heavily methionine-substituted T4 lysozyme as an example, it is shown how the addition or deletion of a small number of methionines can simplify the location of selenium sites for use in MAD phasing. By comparing the X-ray data for a large numb ...
Using heavily methionine-substituted T4 lysozyme as an example, it is shown how the addition or deletion of a small number of methionines can simplify the location of selenium sites for use in MAD phasing. By comparing the X-ray data for a large number of singly substituted lysozymes, it is shown that the optimal amino acid to be substituted by methionine is leucine, followed, in order of preference, by phenylalanine, isoleucine and valine. The identification of leucine as the first choice agrees with the ranking suggested by the Dayhoff mutation probability, i.e. by the frequency of amino-acid substitutions in the sequences of related proteins. The ranking of the second and subsequent choices, however, differ significantly.
Related Citations:
A Test of the "jigsaw-puzzle" Model for Protein Folding by Multiple Methionine Substitutions within the Core of T4 lysozyme Gassner, N.C.,Baase, W.A.,Matthews, B.W. (1996) Proc.Natl.Acad.Sci.USA 93: 12155
Methionine and Alanine Substitutions Show that the Formation of Wild-type-like Structure in the Carboxy-terminal Domain of T4 Lysozyme is a Rate-Limiting Step in Folding Gassner, N.C.,Baase, W.A.,Lindstrom, J.D.,Lu, J.,Dahlquist, F.W.,Matthews, B.W. (1999) Biochemistry 38: 14451
Structure of Bacteriophage T4 Lysozyme Refined at 1.7 A Resolution Weaver, L.H.,Matthews, B.W. (1987) J.Mol.Biol. 193: 189
Organizational Affiliation:
Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, 1229 University of Oregon, Eugene, OR 97403-1229, USA.
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