Article

Crystal structures of Ral-GppNHp and Ral-GDP reveal two binding sites that are also present in Ras and Rap.

Department of Molecular and Structural Biochemistry, 128 Polk Hall-CB 7622, North Carolina State University, Raleigh, NC 27695, USA.
Structure (Impact Factor: 6.79). 12/2004; 12(11):2025-36. DOI: 10.1016/j.str.2004.08.011
Source: PubMed

ABSTRACT RalA is a GTPase with effectors such as Sec5 and Exo84 in the exocyst complex and RalBP1, a GAP for Rho proteins. We report the crystal structures of Ral-GppNHp and Ral-GDP. Disordered switch I and switch II, located away from crystal contacts, are observed in one of the molecules in the asymmetric unit of the Ral-GppNHp structure. In the other molecule in the asymmetric unit, a second Mg(2+) ion is bound to the GppNHp gamma-phosphate in an environment in which switch I is pulled away from the nucleotide and switch II is found in a tight beta turn. Clustering of conserved residues on the surface of Ral-GppNHp identifies two putative sites for protein-protein interaction. One site is adjacent to switch I. The other is modulated by switch II and is obstructed in Ral-GDP. The Ral structures are discussed in the context of the published structures of the Ral/Sec5 complex, Ras, and Rap.

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