The proline-rich P65 protein of Mycoplasma pneumoniae is a component of the Triton X-100-insoluble fraction and exhibits size polymorphism in the strains M129 and FH.
Previously, we described the identification of a novel Mycoplasma pneumoniae M129 protein, named P65 because of its apparent molecular mass of 65 kDa estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (T. Proft and R. Herrmann, Mol. Microbiol. 13:337-348, 1994). DNA sequence analysis of the P65 open reading frame (orfp65), however, revealed an ORF encoding a protein with a molecular weight of 47,034. This discrepancy can be explained by the unusual amino acid composition of this protein. According to the deduced amino acid sequence, the N-terminal half of P65 contains several penta- and hexapeptides (DPNAY and DPNQAY) forming a proline-rich acidic domain. Secondary-structure predictions indicated beta-sheets and turns within that region, suggesting an extended and rigid conformation. Near the C terminus of P65 the tripeptide Arg-Gly-Asp (RGD) was found. This motif is known to play an important role in binding of extracellular matrix proteins to integrins. P65 could be located exclusively to the Triton X-100-insoluble cell fraction. The results of immunofluorescence microscopy and of immunoadsorption experiments indicated that P65 carries surface-exposed regions. Mild treatment of whole cells with proteases resulted in cleavage of a limited amount of P65 molecules, suggesting either that only a small percentage of P65 molecules are exposed on the surface or that protease cleavage is hampered by a compact protein conformation or by binding of an unknown component to P65. P65 exhibits size polymorphism in M. pneumoniae M129 and FH. This is caused by an intragenetic duplication of a 54-bp sequence within the FH orfp65. As a consequence, the number of DPNAY pentapeptides increased from 9 to 12 repeats in the FH strain.
Proft
T
T
Zentrum für Molekulare Biologie Heidelberg, Mikrobiologie, Universität Heidelberg, Germany.
Hilbert
H
H
Layh-Schmitt
G
G
Herrmann
R
R
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry; D005455:Fluorescent Antibody Technique; D007163:Immunosorbent Techniques; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009177:Mycoplasma pneumoniae / Q000737:chemistry* / Q000235:genetics; D017830:Octoxynol; D011110:Polymorphism, Genetic; D012689:Sequence Homology, Nucleic Acid; D012995:Solubility; D013045:Species Specificity
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C093832:Mycoplasma protein 65-kDa; D017830:Octoxynol