The protein encoded by the cro regulator gene of lambda (λ) bacteriophage (q.v.). The cro gene lies alongside C 1 gene, with its promoter to the immediate left. During transcription the host transcriptase moves to the right. Movement of this enzyme can be blocked by the lambda repressor (q.v.), which binds to an operator that overlaps the cro promoter. The cro repressor contains 66 amino acids. The monomers associate in pairs to form the active repressor, which binds to DNA via a helix-term-helix motif (q.v.). The cro repressor is required for the virus to enter the lytic cycle (q.v.). Since the cro repressor represses the lambda repressor, it is sometimes called an antirepressor. See Chronology, 1981, Anderson et al.; regulator gene.
Subjects: Genetics and Genomics.