DNA-BINDING ACTIVITY OF THE C2 PROTEIN OF TOMATO YELLOW LEAF CURL GEMINIVIRUS

The in vitro DNA-binding activity of the C2 protein of tomato yellow l eaf curl geminivirus (TYLCV) was studied following its expression in E scherichia coli as a fusion protein with an His tag N-terminal extensi on (His-C2). Southwestern blotting experiments demonstrated that the C 2 protein is able to bind both single-stranded and double-stranded DNA probes. In electrophoretic mobility shift assays performed using puri fied protein and single-stranded DNA probes several shifted complexes were formed. The presence of NaCl (up to 800 mM) did not substantially affect binding profiles, demonstrating a stable interaction. His-CP a ppeared to bind single-stranded DNA in a sequence-nonspecific manner, with a preference for single-stranded compared to double-stranded DNA. Deletion mutants demonstrated that the central core of C2 (amino acid s 33 to 104), which contains a Cys-His rich region, is sufficient for conferring binding activity. The potential significance of this DNA-bi nding activity with respect to possible biological functions of TYLCV C2 protein is discussed. (C) 1996 Academic Press, Inc.