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KMID : 0578320120330020211
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Molecules and Cells
2012 Volume.33 No. 2 p.211 ~ p.216
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A Mutational Study of Cnu Reveals Attractive Forces between Cnu and H-NS
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Yun Sang-Hoon
Ji Sang-Chun
Jeon Heung-Jin
Wang Xun
Lee Young-Hoon
Choi Byong-Seok
Lim Heon-M.
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Abstract
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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.
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KEYWORD
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Cnu, DNA binding, H-NS, protein-protein interaction
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