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Mol. Cells 2012; 33(2): 211-216
Published online February 15, 2012
https://doi.org/10.1007/s10059-012-0006-5
© The Korean Society for Molecular and Cellular Biology
A Mutational Study of Cnu Reveals Attractive Forces between Cnu and H-NS
Correspondence to : *Correspondence: hmlim@cnu.ac.kr
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 me-chanism 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.
Keywords Cnu, DNA binding, H-NS, protein-protein interaction
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Research Article
Mol. Cells 2012; 33(2): 211-216
Published online February 29, 2012 https://doi.org/10.1007/s10059-012-0006-5
Copyright © The Korean Society for Molecular and Cellular Biology.
A Mutational Study of Cnu Reveals Attractive Forces between Cnu and H-NS
Sang Hoon Yun1, Sang Chun Ji1,3, Heung Jin Jeon1, Xun Wang1, Younghoon Lee2, Byong-Seok Choi2, and Heon M. Lim1,*
1Department of Biology, College of Biological Sciences and Biotechnology, Chungnam National University, Daejeon 305-764, Korea, 2Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea, 3Present address: Department of Pharmacology and Clinical Pharmacology, Seoul National University College of Medicine and Hospital, Seoul 110-799, Korea
Correspondence to:*Correspondence: hmlim@cnu.ac.kr
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 me-chanism 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.
Keywords: Cnu, DNA binding, H-NS, protein-protein interaction
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