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J. Bacteriol., Apr 1997, 2668-2677, Vol 179, No. 8
DC Krause, T Proft, CT Hedreyda, H Hilbert, H Plagens and R Herrmann
A new genetic locus associated with Mycoplasma pneumoniae cytadherence was
previously identified by transposon mutagenesis with Tn4001. This locus
maps approximately 160 kbp from the genes encoding cytadherence- associated
proteins HMW1 and HMW3, and yet insertions therein result in loss of these
proteins and a hemadsorption-negative (HA-) phenotype, prompting the
designation cytadherence-regulatory locus (crl). In the current study,
passage of transformants in the absence of antibiotic selection resulted in
loss of the transposon, a wild-type protein profile, and a HA+ phenotype,
underscoring the correlation between crl and M. pneumoniae cytadherence.
Nucleotide sequence analysis of crl revealed open reading frames (ORFs)
orfp65, orfp216, orfp41, and orfp24, arranged in tandem and flanked by a
promoter-like and a terminator-like sequence, suggesting a single
transcriptional unit, the P65 operon. The 5' end of orfp65 mRNA was mapped
by primer extension, and a likely promoter was identified just upstream.
The product of each ORF was identified by using antisera prepared against
fusion proteins. The previously characterized surface protein P65 is
encoded by orfp65, while the 190,000 Mr cytadherence-associated protein
HMW2 is a product of orfp216. Proteins with sizes of 47,000 and 41,000 Mr
and unknown function were identified for orfp41 and orfp24, respectively.
Structural analyses of HMW2 predict a periodicity highly characteristic of
a coiled-coil conformation and five leucine zipper motifs, indicating that
HMW2 probably forms dimers in vivo, which is consistent with a structural
role in cytadherence. Each transposon insertion mapped to orfp216 but
affected the levels of all products of the P65 operon. HMW2 is thought to
form a disulfide-linked dimer, formerly designated HMW5, and examination of
an hmw2 deletion mutant confirms that HMW5 is a product of the hmw2 gene.
Copyright © 1997, American Society for Microbiology
Transposon mutagenesis reinforces the correlation between Mycoplasma pneumoniae cytoskeletal protein HMW2 and cytadherence
Department of Microbiology, University of Georgia, Athens 30602, USA. dkrause@uga.cc.uga.edu
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