The virulence-associated protein HsvA from the fire blight pathogen is a polyamine amidinotransferase.

Studies of virulence determinants in the bacterial phytopathogen , the cause of devastating fire blight disease in apple and pear, have shown that HsvA, a putative amidinotransferase enzyme located in the Hrp pathogenicity island, is required for systemic infection in apple. However, the mechanism by which HsvA contributes to virulence is unclear. To investigate the role of HsvA in virulence, we carried out a series of biochemical and structural studies to characterize the amidinotransferase activity of HsvA.