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Infect. Immun., 04 1995, 1340-1348, Vol 63, No. 4
CT Gonzalez, SK Maheswaran and MP Murtaugh
An ssa1-homologous genomic fragment cloned from Pasteurella haemolytica
serotype 2 (ST2) enabled transformation of Escherichia coli DH5 alpha to a
serotype 1 (ST1) phenotype through expression of the ST1-specific antigen
(Ssa1). The Ssa1 protein expressed by ssa1-transformed E. coli was
susceptible to heat and protease treatment and was distinct from P.
haemolytica ST1-specific capsular polysaccharide. Electrophoretic analysis
of in vitro-translated proteins, as well as the predicted amino acid
sequence, demonstrated that Ssa1 proteins encoded from either ST1- or
ST2-derived ssa1 genes were essentially identical. A comparison of the
nucleotide sequences of ssa1 genes derived from P. haemolytica ST1 and ST2
revealed greater than 99% homology. Amino acid sequence homology of the
predicted products of ST1- and ST2-derived ssa1 genes was greater than 98%.
Northern (RNA) blot studies revealed that the presence of an increased
level of ssa1 transcript in P. haemolytica ST1 grown as surface-adherent
cultures on solid medium was correlated with a serologically detectable
Ssa1 protein. Expression of the ssa1 transcript in ST1 was similarly
upregulated by a high iron concentration in the growth medium.
Copyright © 1995, American Society for Microbiology
Pasteurella haemolytica serotype 2 contains the gene for a noncapsular serotype 1-specific antigen
Department of Veterinary PathoBiology, University of Minnesota, St. Paul 55108.
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