. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MUSSEL CYSTINE-RICH DOPA PROTEINS 129 o c CO. 100 80 60 'C 40 « 20 20 40 Elution Time (min) Figure 3. HPLC chromatography profiles of control Mefp-2 —), and CAMC-Mefp-2 ( ) and COMC-Mefp-2 ( ), reduced and alkylated as indicated in Materials and Methods, and mon- itored at 280 nm. Proteins were resolved on a x 25 cm analytical C8 column using the same gradient program as shown in Figure 2 (inclined dashed line). Concentration of control Mefp-2 was half that of the al- kvlated derivatives, but the detector attenuation wa
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MUSSEL CYSTINE-RICH DOPA PROTEINS 129 o c CO. 100 80 60 'C 40 « 20 20 40 Elution Time (min) Figure 3. HPLC chromatography profiles of control Mefp-2 —), and CAMC-Mefp-2 ( ) and COMC-Mefp-2 ( ), reduced and alkylated as indicated in Materials and Methods, and mon- itored at 280 nm. Proteins were resolved on a x 25 cm analytical C8 column using the same gradient program as shown in Figure 2 (inclined dashed line). Concentration of control Mefp-2 was half that of the al- kvlated derivatives, but the detector attenuation was halved. of similar mobility were often apparent. All reacted pos- itively with the NBT and odiphenol-specific Arnow stains (not shown), consistent with presence of DOPA in the amino acid composition. Mefp-2, resolved by SDS-PAGE (see below), did not stain with the PAS procedure for cis- diol sugars, though control proteins in the same gel were PAS-positive, suggesting that Mefp-2. in common with Mefp-1, is not a glycoprotein. The most dramatic compositional difference between Mefp-1 and -2 (Table I) is the occurrence of cystine ex- clusively in Mefp-2 and at remarkably high levels (6-7 mol %). A comparison of native Mefp-2 with reduced and S-carbamidomethylated protein (CAMC-Mefp-2), to- gether with the exceedingly low levels of S-carboxyme- thylcysteine in the acid hydrolysates of native Mefp-2 that had been treated with iodoacetamide in or 6 M urea without prior reduction by DTT, shows that most of the S-alkylated cysteine (ca. 15 mol %) had originally been in the disulphide form. The DOPA content of Mefp-2 (2- 3 mol %) was much lower than that of Mefp-1 (11-18%) and, unlike other molluscan DOPA proteins (Rzepecki ct ui. 1991), the Lys:DOPA ratio far exceeded unity. Both contained proline, but no hydroxylation to 3- and 4-Hyp occurred in Mefp-2. Glycine, rare in Mefp-1, made up about 14 mol % of Mefp-2. Elevated levels (about 5-fold) of Asx and Glx, and lower levels
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