Population shift vs induced fit: The case of bovine seminal ribonuclease swapping dimer
✍ Scribed by Antonello Merlino; Luigi Vitagliano; Filomena Sica; Adriana Zagari; Lelio Mazzarella
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2004
- Tongue
- English
- Weight
- 221 KB
- Volume
- 73
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
Bovine seminal ribonuclease (BS‐RNase) is a unique member of the pancreatic‐like ribonuclease superfamily. This enzyme exists as two conformational isomers with distinctive biological properties. The structure of the major isomer is characterized by the swapping of the N‐terminal segment (M×M BS‐RNase). In this article, the crystal structures of the ligand‐free M×M BS‐RNase and its complex with 2′‐deoxycitidylyl(3′,5′)‐2′‐deoxyadenosine derived from isomorphous crystals have been refined. Interestingly, the comparison between this novel ligand‐free form and the previously published sulfate‐bound structure reveals significant differences. In particular, the ligand‐free M×M BS‐RNase is closer to the structure of M×M BS‐RNase productive complexes than to the sulfate‐bound form. These results reveal that M×M BS‐RNase presents a remarkable flexibility, despite the structural constraints of the interchain disulfide bridges and the swapping of the N‐terminal helices. These findings have important implications to the ligand binding mechanism of M×M BS‐RNase. Indeed, a population shift rather than a substrate‐induced conformational transition may occur in the M×M BS‐RNase ligand binding process. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004