Affiliation:
1. Department of Microbiology, University of Georgia, Athens, Georgia 30602,1 and
2. ZMBH, Mikrobiologie, Universität Heidelberg, 69120 Heidelberg, Germany2
Abstract
ABSTRACT
Mycoplasma pneumoniae
cytadherence is mediated by a specialized, polar attachment organelle. Certain spontaneously arising cytadherence mutants (designated class I) lack HMW2, fail to localize the adhesin protein P1 to the attachment organelle, and exhibit accelerated turnover of proteins HMW1, HMW3, and P65. Insertional inactivation of
hmw2
by Tn
4001
results in a phenotype nearly identical to that of the class I mutants, suggesting that the latter may result from a defect in
hmw2
. In this study, the recombinant wild-type
hmw2
allele successfully complemented a class I mutant when introduced by transposon delivery. Synthesis of recombinant HMW2 at wild-type levels resulted in reacquisition of hemadsorption and normal levels of HMW1, HMW3, and P65. Low-level production of HMW2 in some transformants resulted in only an intermediate capacity to hemadsorb. Furthermore, full restoration of HMW1 and P65, but not that of HMW3, was directly proportional to the amount of recombinant HMW2 produced, reflecting the importance of proper stoichiometry for certain cytadherence-associated proteins. The recombinant class I
hmw2
allele did not restore cytadherence, consistent with a defect in
hmw2
in this mutant. A frameshift was discovered in different oligoadenine tracts in
hmw2
from two independent class I mutants. Finally, protein P28 is thought to be the product of internal translation initiation in
hmw2
. A transposon excision-deletion mutant produced a truncated HMW2 but no P28, consistent with this conclusion. However, this deletion mutant was hemadsorption positive, indicating that P28 may not be required for cytadherence.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
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