1AYI

COLICIN E7 IMMUNITY PROTEIN IM7

1AYI の概要

• エントリーDOI: 10.2210/pdb1ayi/pdb
• 分子名称: COLICIN E IMMUNITY PROTEIN 7 (2 entities in total)
• 機能のキーワード: bacteriocin, e colicins, protein-protein interactions, dnase inhibitor
• 由来する生物種: Escherichia coli
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 9906.96

構造登録者

Dennis, C.A.,Pauptit, R.A.,Wallis, R.,James, R.,Moore, G.R.,Kleanthous, C. (登録日: 1997-11-04, 公開日: 1998-01-28, 最終更新日: 2024-04-03)

主引用文献

Dennis, C.A.,Videler, H.,Pauptit, R.A.,Wallis, R.,James, R.,Moore, G.R.,Kleanthous, C.
A structural comparison of the colicin immunity proteins Im7 and Im9 gives new insights into the molecular determinants of immunity-protein specificity.
Biochem.J., 333 ( Pt 1):183-191, 1998

PubMed Abstract: We report the first detailed comparison of two immunity proteins which, in conjunction with recent protein engineering data, begins to explain how these structurally similar proteins are able to bind and inhibit the endonuclease domain of colicin E9 (E9 DNase) with affinities that differ by 12 orders of magnitude. In the present work, we have determined the X-ray structure of the Escherichia coli colicin E7 immunity protein Im7 to 2.0 A resolution by molecular replacement, using as a trial model the recently determined NMR solution structure of Im9. Whereas the two proteins adopt similar four-helix structures, subtle structural differences, in particular involving a conserved tyrosine residue critical for E9 DNase binding, and the identity of key residues in the specificity helix, lie at the heart of their markedly different ability to bind the E9 DNase. Two other crystal structures were reported recently for Im7; in one, Im7 was a monomer and was very similar to the structure reported here, whereas in the other it was a dimer to which functional significance was assigned. Since this previous work suggested that Im7 could exist either as a monomer or a dimer, we used analytical ultracentrifugation to investigate this question further. Under a variety of solution conditions, we found that Im7 only ever exists in solution as a monomer, even up to protein concentrations of 15 mg/ml, casting doubt on the functional significance of the crystallographically observed dimer. This work provides a structural framework with which we can understand immunity-protein specificity, and in addition we believe it to be the first successfully refined crystal structure solved by molecular replacement using an NMR trial model with less than 100% sequence identity.

PubMed: 9639578

実験手法

X-RAY DIFFRACTION (2 Å)