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A group A streptococcal Enn protein potentially resulting from intergenomic recombination exhibits atypical immunoglobulin‐binding characteristics
Author(s) -
Podblelski A.,
Hawlitzky J.,
Pack T. D.,
Flosdorff A.,
Boyle M. D. P.
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb01060.x
Subject(s) - biology , gene , homology (biology) , recombinant dna , microbiology and biotechnology , open reading frame , streptococcus pyogenes , escherichia coli , genetics , peptide sequence , bacteria , staphylococcus aureus
Summary The gene encoding the Enn protein ( enn ) of the M untypeable group A streptococcal (GAS) strain 64/14 was amplified by polymerase chain reaction, cloned into the expression vector pJLA602 and expressed in Escherichia coli DH5α. Unlike other GAS–Enn proteins, which exhibit IgA‐binding activity, the recombinant Enn enn 64/14 protein reacted preferentially with human IgG 3 . The 1050 bp open reading frame comprising the enn 64/14 gene was completely sequenced. The region of the gene encoding the signal peptide and the C ‐terminus exhibited >95% homology to corresponding sections of other enn genes. The region of enn 64/74 encoding the N ‐terminus of the mature Enn protein was found to be highly homologous to the corresponding section of the gene encoding the M‐like protein of GAS serotype M9 ( emmL 9). The reoombinant protein encoded by emmL 9 was found to react with all four human IgG subclasses. About 30% of the 1152bp open reading frame of emmiL 9 encoding the N ‐terminus was found to display >90% homology to the corresponding section of enn 64/14 but was <50% homologous in the remainder of the gene sequence. The functional analysis of the subcloned N ‐terminal section of emmL 9 demonstrated a polypeptide exhibiting selective binding to human IgG 3 . These findings suggested that enn 64/14 was a hybrid gene formed by recombination of an enn gene and an emmL 9 gene. The putative recombinational event could have Involved a set of flanking 7bp direct repeats. Since enn 64/14 and emmL 9 are genes from different phylogenetic lineages of GAS, this report provides evidence that intergenomic recombinations between different types of GAS genes can occur and could lead to hybrid proteins with unique Ig‐binding characteristics.