title: Accessibility of tryptophan residues in immunoglobulin M as an index of its conformational changeability.
abstract: 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.
authors.affiliation: N.D. Zelinsky Institute of Organic Chemistry, USSR Academy of Sciences, Moscow.
authors.forename: V A
authors.initials: VA
authors.lastname: Lapuk
authors.forename: A I
authors.initials: AI
authors.lastname: Tchukhrova
authors.forename: N M
authors.initials: NM
authors.lastname: Katiashvili
authors.forename: F V
authors.initials: FV
authors.lastname: Shmakova
authors.forename: E D
authors.initials: ED
authors.lastname: Kaverzneva
authors.forename: V P
authors.initials: VP
authors.lastname: Timofeev
mesh_terms: D015077:2-Hydroxy-5-nitrobenzyl Bromide; D004578:Electron Spin Resonance Spectroscopy; D006026:Glycoside Hydrolases; D007075:Immunoglobulin M / Q000737:chemistry*; D011487:Protein Conformation; D012995:Solubility; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D007075:Immunoglobulin M; D015077:2-Hydroxy-5-nitrobenzyl Bromide; D014364:Tryptophan; D006026:Glycoside Hydrolases