THE PROLINE-RICH P65 PROTEIN OF MYCOPLASMA-PNEUMONIA IS A COMPONENT OF THE TRITON X-100-INSOLUBLE FRACTION AND EXHIBITS SIZE POLYMORPHISM IN THE STRAINS M129 AND FH
T. Proft et al., THE PROLINE-RICH P65 PROTEIN OF MYCOPLASMA-PNEUMONIA IS A COMPONENT OF THE TRITON X-100-INSOLUBLE FRACTION AND EXHIBITS SIZE POLYMORPHISM IN THE STRAINS M129 AND FH, Journal of bacteriology, 177(12), 1995, pp. 3370-3378
Previously, we described the identification of a novel Mycoplasma pneu
moniae M129 protein, named P65 because of its apparent molecular mass
of 65 kDa estimated by sodium dodecyl sulfate polyacrylamide gel elect
rophoresis (T. Proft and R, Herrmann, Mel. Microbiol. 13:337-348, 1994
). DNA sequence analysis of the P65 open reading frame (orfp65), howev
er, revealed an ORF encoding a protein with a molecular weight of 47,0
34, This discrepancy can be explained by the unusual amino acid compos
ition of this protein, According to the deduced amino acid sequence, t
he N-terminal half of P65 contains several penta- and hexapeptides (DP
NAY and DPNQAY) forming a proline-rich acidic domain. Secondary-struct
ure predictions indicated beta-sheets and turns within that region, su
ggesting an extended and rigid conformation. Near the C terminus of P6
5 the tripeptide Arg-Gly-Asp (RGD) was found, This motif is known to p
lay an important role in binding of extracellular matrix proteins to i
ntegrins. P65 could be located exclusively to the Triton X-100-insolub
le cell fraction, The results of immunofluorescence microscopy and of
immunoadsorption experiments indicated that P65 carries surface-expose
d regions. Mild treatment of whole cells with proteases resulted in cl
eavage of a limited amount of P65 molecules, suggesting either that on
ly a small percentage of P65 molecules are exposed on the surface or t
hat protease cleavage is hampered by a compact protein conformation or
by binding of an unknown component to P65, P65 exhibits size polymorp
hism in Ill. pneumoniae M129 and FH. This is caused by an intragenetic
duplication of a 54-bp sequence within the FH orfp65. As a consequenc
e, the number of DPNAY pentapeptides increased from 9 to 12 repeats in
the FH strain.