Incomplete activation of Escherichia coli hemolysin (HlyA) due to mutations in the 3' region of hlyC. |
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| Authors: | C Guzmn-Verri F García and S Arvidson |
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| Affiliation: | C Guzmán-Verri, F García, and S Arvidson |
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| Abstract: | Mutational analysis of the carboxy-terminal region of Escherichia coli HlyC was performed by site-directed mutagenesis. Replacement of residue Val-127 or Lys-129 reduced the activity of HlyC to about 30 or 60%, respectively, of that of the wild type, while replacement of Gly-128 reduced the activity to less than 1% of the wild-type level. Complete inactivation of HlyC was caused by a double mutation, replacement of Gly-128 with valine and of Lys-129 with isoleucine. Analysis of culture supernatants from mutants with reduced hemolytic activity by two-dimensional gel electrophoresis revealed the production and simultaneous secretion of nonacylated, monoacylated, and fully acylated HlyA forms, demonstrating impairment of the acylation reaction, possibly due to a decreased affinity of HlyC for the individual HlyA acylation sites. |
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