title: A2 cro, the lysogenic cycle repressor, specifically binds to the genetic switch region of Lactobacillus casei bacteriophage A2.
abstract: Lysogenic induction of temperate bacteriophage A2 of Lactobacillus casei is controlled by the action of its cI and cro products at the phage operator region. Three 20-bp inverted repeated DNA segments (subsites O1, O2, and O3) and the two divergent (PL and PR) promoters were mapped within the 153-bp operator region. The A2-encoded Cro product is shown to be the functional homolog of lambda Cro. The binding of Cro to the three operator subsites is noncooperative and yields two discrete protein-DNA complexes of retarded migration in mobility shift assays. The Kapp value for the Cro-PL-PR DNA complex was estimated to be 6 nM. Cro shows a slightly higher affinity for O3 than for O1 and O2 subsites. The O3 subsite overlaps the -35 hexamer of the PL promoter, which directs cI expression. A Cro mutant protein, devoid of the last 12 residues (Cro*), allowed the assignment of the DNA-binding domain to the NH2 end of Cro. The C end enhances its affinity for the DNA and probably stabilizes bending induced by Cro.
authors.affiliation: Facultad de Medicina, Universidad de Oviedo, Julián Clavería s.n., Oviedo, 33006, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Ladero
authors.forename: P
authors.initials: P
authors.lastname: García
authors.forename: J C
authors.initials: JC
authors.lastname: Alonso
authors.forename: J E
authors.initials: JE
authors.lastname: Suárez
mesh_terms: D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D018983:DNA Footprinting; D004279:DNA, Viral / Q000378:metabolism; D005812:Genes, Switch / Q000235:genetics; D007780:Lacticaseibacillus casei / Q000235:genetics / Q000821:virology*; D008242:Lysogeny / Q000235:genetics*; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D004279:DNA, Viral; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins