Entry exclusion (Eex) is a process which prevents redundant transfer of DNA between donor cells. TraS is a protein involved in Eex. It blocks redundant conjugative DNA synthesis and transport between donor cells, and it is suggested that TraS interferes with a signalling pathway that is required to trigger DNA transfer [1]. TraS on the recipient cell is known to form an interaction with TraG on the donor cell [1].

1: Entry exclusion in F-like plasmids requires intact TraG in the donor that recognizes its cognate TraS in the recipient. Audette GF, Manchak J, Beatty P, Klimke WA, Frost LS; Microbiology. 2007;153:442-451. PMID:17259615