title: A mutational study of Cnu reveals attractive forces between Cnu and H-NS.
abstract: Cnu is a small 71-amino acid protein that complexes with H-NS and binds to a specific sequence in the replication origin of the E. coli chromosome. To understand the mechanism of interaction between Cnu and H-NS, we used bacterial genetics to select and analyze Cnu variants that cannot complex with H-NS. Out of 2,000 colonies, 40 Cnu variants were identified. Most variants (82.5%) had a single mutation, but a few variants (17.5%) had double amino acid changes. An in vitro assay was used to identify Cnu variants that were truly defective in H-NS binding. The changes in these defective variants occurred exclusively at charged amino acids (Asp, Glu, or Lys) on the surface of the protein. We propose that the attractive force that governs the Cnu-H-NS interaction is an ionic bond, unlike the hydrophobic interaction that is the major attractive force in most proteins.
authors.affiliation: Department of Biology, College of Biological Sciences and Biotechnology, Chungnam National University, Daejeon, 305-764, Korea.
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Yun
authors.forename: Sang Chun
authors.initials: SC
authors.lastname: Ji
authors.forename: Heung Jin
authors.initials: HJ
authors.lastname: Jeon
authors.forename: Xun
authors.initials: X
authors.lastname: Wang
authors.forename: Younghoon
authors.initials: Y
authors.lastname: Lee
authors.forename: Byong-Seok
authors.initials: BS
authors.lastname: Choi
authors.forename: Heon M
authors.initials: HM
authors.lastname: Lim
mesh_terms: D000595:Amino Acid Sequence; D004252:DNA Mutational Analysis; D004261:DNA Replication; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D011487:Protein Conformation
chemical_list: C505237:Cnu protein, E coli; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C529458:FimG protein, E coli; D036781:Fimbriae Proteins