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PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase
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Accessibility of tryptophan residues in immunoglobulin M as an index of its conformational changeability

V A Lapuk1, A I Tchukhrova, N M Katiashvili

  • 1N.D. Zelinsky Institute of Organic Chemistry, USSR Academy of Sciences, Moscow.

Journal of Biomolecular Structure & Dynamics
|December 1, 1990
PubMed

Demonstrated herein is the possibility of using the accessibility of tryptophan (Trp) residues in immunoglobulin M (IgM) upon modification with Koshland reagent (2-hydroxy-5-nitrobenzyl bromide) as an index of the conformational changeability of IgM. Of fourteen Trp's in the native IgM (per HL-region) only one appeared to be most accessible, evidently Trp312 in the mu-chain. Irreversible acidic and thermal conformational transitions in IgM increase the number of accessible Trp's approximately two-fold. Following partial enzymatic deglycosylation of IgM, deep scission of mannose in particular, all Trp's become inaccessible. Modification of the most accessible Trp increases 2-3 fold the number of tyrosine residues readily accessible upon nitration with tetranitromethane. Modification of four trp's using spin-label method data causes a sharp reduction of the mobility of the C mu 3 domain and a simultaneous decrease in the solubility of modified IgM.

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