Comparison of the Proteins and Polypeptides of the Eight Serotypes of Ureaplasma urealyticum by Isoelectric Focusing and Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis

Abstract

Analysis of representative strains of the 8 human serotypes of U. urealyticum by polyacrylamide gel electrophoresis identified 36-40 polypeptides for each strain. At least 80% of the peptides were common among strains, but unique major peptides were identifiable in ureaplasmic types. Type 1 had a polypeptide of 85,000 daltons, type 3 had a polypeptide of 72,000 daltons, type 5 had a polypeptide of 64,000 daltons and type 8 had a polypeptide of 95,000 daltons. The unique polypeptides in types 1 and 8 were identified as membrane components. Two common major components of 44,000 and 70,000 daltons were observed. Several components were common to some, but not all, serotypes. Patterns obtained from U. urealyticum strains were strikingly different from the patterns of Acholeplasma laidlawii, Mycoplasma gallisepticum, M. arginini and M. hominis. Isoelectric focusing demonstrated a unique membrane protein for type 1 at pK 6.4, whereas type 8 possessed an assembly of 5 unique proteins at pK 7.0. Ureaplasmata were strongly similar to each other by isoelectric focusing, but strikingly different from members of the other genera studied. Although a filtered, strong buffered dialysate medium with 1% serum and 30 mM urea was used both to maximize yields and to minimize contamination, minor contaminants were detected, which comigrated with horse transferrin (pK 6.0) and cytochrome c (MW 14,000). The similarities of the polypeptide patterns of U. urealyticum strains affirm their close relationships to each other, in contrast to the diversity shown in the genus Mycoplasma, and the recognition of type-specific membrane peptides will enhance the identification of serotypes and the classification of strains.