Investigation of a Zα-like Peptide Motif in Koi Herpesvirus

Koi herpesvirus (KHV) is responsible for high mortality in the common carp, a global food staple of which over 1.5 million metric tons is harvested annually. The objective of this study is to investigate B-DNA interactions with a hypothesized Zα, or Z-DNA binding, domain in the KHV open reading frame 112 (ORF112) peptide motif. Mutations analogous to the Y84A and N62D mutations have been shown to be critical for Z-DNA binding in proteins with Zα domains. Therefore, circular dichroism (CD) spectra were collected of the wild type (WT), Y84A mutant, and N62D mutant ORF112 proteins titrated into poly(dGdC) and calf thymus B-DNA. The WT and Y84A mutant proteins bound to two distinct DNA conformations that did not indicate a Bto Z-DNA transition, and the N62D mutation prevented any conformational change. The results indicate that B-DNA interacts with the Zα-like peptide motif in a non-sequence specific manner to form a unique structure that requires the Asn 62 residue and is affected structurally by the Tyr 84 residue.