Investigation of a Zα-like Peptide Motif in Koi Herpesvirus


Amy Chyao, Harvard College ‘14
Ky Lowenhaupt, Department of Biology, Massachusetts Institute of Technology

Abstract

Koi herpesvirus (KHV) is responsible for high mortality in the common carp and koi fish. The objective of this study is to investigate the interactions of a hypothesized Zα, or Z-DNA binding, domain in the KHV open reading frame 112 (ORF112) peptide motif with B-DNA to determine if a transition to Z-DNA occurs. When Y84A and N62D mutations are made in proteins that contain Zα domains, Z-DNA binding is compromised, so these amino acids are critical for Z-DNA binding. 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 to analyze the protein-DNA bound structures. The WT and Y84A mutant proteins bound to two distinct DNA conformations that did not indicate a B- to 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.

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