Article abstract
Nature Cell Biology 1, 106 - 112 (1999)
Published online: 15 May 1999 | doi:10.1038/10076
Structure of the Janus-faced C2B domain of rabphilin
Josep Ubach1, Jesús García1, M. Paige Nittler1,3, Thomas C. Südhof2 & Josep Rizo1
Abstract
C2 domains are widespread protein modules that often occur as
tandem repeats in many membrane-trafficking proteins such as synaptotagmin
and rabphilin. The first and second C2 domains (C2A
and C2B, respectively) have a high degree of homology but also
specific differences. The structure of the C2A domain of synaptotagmin
I has been extensively studied but little is known about the C2B
domains. We have used NMR spectroscopy to determine the solution structure
of the C2B domain of rabphilin. The overall structure of the C
2B domain is very similar to that of other C2 domains, with
a rigid 
-sandwich core and loops at the top (where Ca2+
binds) and the bottom. Surprisingly, a relatively long 
-helix is inserted
at the bottom of the domain and is conserved in all C2B domains.
Our results, together with the Ca2+-independent interactions
observed for C2B domains, indicate that these domains have a Janus-faced
nature, with a Ca2+-binding top surface and a Ca2+-independent
bottom surface.
- Departments of Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard , Dallas, Texas 75235,USA
- Department of Molecular Genetics, Howard Hughes Medical Institute and Center for Basic Neuroscience, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas , Texas 75235, USA
- Present address: University of California at San Francisco , 513 Parnassus Avenue, Box 0450, San Francisco , California 94143, USA
Correspondence to: Josep Rizo1 e-mail: jose@arnie.swmed.edu
