title: Crystal structure of the restriction-modification system control element C.Bcll and mapping of its binding site.
abstract: Protection from DNA invasion is afforded by restriction-modification systems in many bacteria. The efficiency of protection depends crucially on the relative expression levels of restriction versus methytransferase genes. This regulation is provided by a controller protein, named C protein. Studies of the Bcll system in E. coli suggest that C.Bcll functions as a negative regulator for M.Bcll expression, implying that it plays a role in defense against foreign DNA during virus infection. C.Bcll binds (Kd = 14.3 nM) to a 2-fold symmetric C box DNA sequence that overlaps with the putative -35 promoter region upstream of the bcllM and bcllC genes. The C.Bcll fold comprises five alpha helices: two helices form a helix-turn-helix motif, and the remaining three helices form the extensive dimer interface. The C.Bcll-DNA model proposed suggests that DNA bending might play an important role in gene regulation, and that Glu27 and Asp31 in C.Bcll might function critically in the regulation.
authors.affiliation: UCLA-DOE Laboratory of Structural Biology and Molecular Medicine, 205 Boyer Hall, Box 951570, Los Angeles, California 90095, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Sawaya
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Zhu
authors.forename: Fana
authors.initials: F
authors.lastname: Mersha
authors.forename: Siu-Hong
authors.initials: SH
authors.lastname: Chan
authors.forename: Rajesh
authors.initials: R
authors.lastname: Dabur
authors.forename: Shuang-Yong
authors.initials: SY
authors.lastname: Xu
authors.forename: Ganesaratnam K
authors.initials: GK
authors.lastname: Balendiran
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites; D003461:Crystallography; D015280:DNA Restriction-Modification Enzymes / Q000235:genetics*; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics; D005786:Gene Expression Regulation; D019077:Helix-Turn-Helix Motifs; D008969:Molecular Sequence Data; D011487:Protein Conformation; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D015280:DNA Restriction-Modification Enzymes; D014157:Transcription Factors