DNA-Binding Activities in Streptococcus gordonii: Identification of a Receptor-Nickase and a Histonelike Protein

Abstract.

Extraction of Streptococcus gordonii cells with the mild chaotropic agent, LiCl, drastically decreased DNA transforming ability, had little effect on viability, and released both DNA nicking and binding activities. Both activities were Mg²⁺ and Ca²⁺ independent and were not competence specific. Southwestern blot analysis of the extract identified putative surface proteins of 56 kDa and 68 kDa in strain Challis and Wicky, respectively. Extracts also contained a 10-kDa DNA-binding protein, designated HSgo, that belongs to the eubacterial histonelike class of proteins.