Divalent Cations Stabilize the α1β1 Integrin I Domain
| Autor: | Sarah Ryan, S.Y. Venyaminov, Christopher D. Benjamin, Mohammad Zafari, Philip Gotwals, Gloria Chi-Rosso, J Singh, Irene Sizing, R B Pepinsky, Victor Koteliansky |
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| Rok vydání: | 1999 |
| Předmět: | |
| Zdroj: | Biochemistry. 38:8280-8288 |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | Recent structural and functional analyses of alpha integrin subunit I domains implicate a region in cation and ligand binding referred to as the metal ion-dependent adhesion site (MIDAS). Although the molecular interactions between Mn2+ and Mg2+ and the MIDAS region have been defined by crystallographic analyses, the role of cation in I domain function is not well understood. Recombinant alpha 1 beta 1 integrin I domain (alpha1-I domain) binds collagen in a cation-dependent manner. We have generated and characterized a panel of antibodies directed against the alpha1-I domain, and selected one (AJH10) that blocks alpha 1 beta 1 integrin function for further study. The epitope of AJH10 was localized within the loop between the alpha 3 and alpha 4 helices which contributes one of the metal coordination sites of the MIDAS structure. Kinetic analyses of antibody binding to the I domain demonstrate that divalent cation is required to stabilize the epitope. Denaturation experiments demonstrate that cation has a dramatic effect on the stabilization of the I domain structure. Mn2+ shifts the point at which the I domain denatures from 3.4 to 6.3 M urea in the presence of the denaturant, and from 49.5 to 58.6 degrees C following thermal denaturation. The structural stability provided to the alpha1-I domain by divalent cations may contribute to augmented ligand binding that occurs in the presence of these cations. |
| Databáze: | OpenAIRE |
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