Crystal structure of tandem type III fiibronectin domains from drosophila neuroglian at 2.0 Å
We report the crystal structure of two adjacent fibronectin type III repeats from the Drosophila neural cell adhesion molecule neuroglian. Each domain consists of two antiparallel 0 sheets and is folded topologically identically to single fibronectin type III domains from the extracellular matrix proteins tenascin and fibronectin. β bulges and left-handed polyproline II helices disrupt the regular β sheet structure of both neuroglian domains. The hydrophobic interdomain interface includes a metalbinding site, presumably involved in stabilizing the relative orientation between domains and predicted by sequence comparision to be present in the vertebrate homolog molecule L1. The neuroglian domains are related by a near perfect 2-fold screw axis along the longest molecular dimension. Using this relationship, a model for arrays of tandem fibronectin type III repeats in neuroglian and other molecules is proposed.
© 1994 Cell Press. Received 4 November 1994, Revised 21 January 1995. We thank Michael Blum for help with freezing crystals; Michael Blum and the staff at CHESS for assistance with data collection; Alfonso Mondragón for programs and advice during data processing; Barbara Hsu for her Patterson search program; Art Chirino and Bill Weis for advice during refinement; Dan Leahy, Wayne Hendrickson, and Harold Erickson for the Tnfn3 coordinates and many helpful discussions; Abraham De Vos for the human growth hormone receptor coordinates; Bill Lane and the Harvard Microchemical Facility for mass spec and other analyses; the Caltech Microchemical Facility for N-terminal sequence analyses; Peer Bork for aligned sequences of Fn-III repeats; Roland Strong for making Figure 3B; Douglas Rees for helpful discussions about metal sites; and our colleagues for critical reading of the manuscript. The program X-PLOR was run on a CRA Y-YMP at the San Diego Supercomputer Center, supported by the National Science Foundation. This work was supported by the Howard Hughes Medical Institute (P.J.B.), a Howard Hughes Medical Institute predoctoral fellowship (A.H.H.), the National Science Foundation (IBN-9120981 to A.J.B.), the American Cancer Society (IRG IN-17 to A.J.B.), and the Purdue Research Foundation (A.J.B.). Coordinates will be deposited with the Brookhaven Protein Data Bank. Until processing is complete. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC Section 1734 solely to indicate this fact.