Kayyem, Jon Faiz and Roman, Janet M. and de la Rosa, Enrique J. and Schwarz, Uli and Dreyer, William J. (1992) Bravo/Nr-CAM Is Closely Related to the Cell Adhesion Molecules L1 and Ng-CAM and Has a Similar Heterodimer Structure. Journal of Cell Biology, 118 (5). pp. 1259-1270. ISSN 0021-9525. http://resolver.caltech.edu/CaltechAUTHORS:20120329-074034688
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Diverse cell-surface molecules of the nervous system play an important role in specifying cell interactions during development. Using a method designed to generate mAbs against neural surface molecules of defined molecular weight, we have previously reported on the surface protein, Bravo, found in the developing avian retinotectal system. Bravo is immunologically detected on developing optic fibers in the retina, but absent from distal regions of the same fibers in the tectum. We have isolated cDNA clones encompassing the entire coding region of Bravo, including clones containing five alternative sequences of cDNA. These putative alternatively spliced sequences encode stretches of polypeptide ranging in length from 10-93 amino acids and are predicted to be both extra- and intracellular. The deduced primary structure of Bravo reveals that, like the cell adhesion molecules (CAMs) chicken Ng- CAM and mouse L1, Bravo is composed of six Ig-like domains, five fibronectin type III repeats, a transmembrane domain, and a short cytoplasmic region. Recently, the cDNA sequence of a related molecule, Nr-CAM, was reported and its possible identity with Bravo discussed (Grumet, M., V. Mauro, M. P. Burgoon, G. E. Edelman, and B. A. Cunningham. 1991. J. Cell Biol. 113:1399-1412). Here we confirm this identity and moreover show that Bravo is found on Muller glial processes and end-feet in the developing retina. In contrast to the single polypeptide chain structure of Nr-CAM reported previously, we show that Bravo has a heterodimer structure composed of an alpha chain of M(r) 140/130 and a beta chain of 60-80 kD. As with L1 and Ng-CAM, the two chains of Bravo are generated from an intact polypeptide by cleavage at identical locations and conserved sites within all three molecules (Ser-Arg/Lys-Arg). The similar domain composition and heterodimer structure, as well as the 40% amino acid sequence identity of these molecules, defines them as an evolutionarily related subgroup of CAMs. The relationship of Bravo to molecules known to be involved in cell adhesion and process outgrowth, combined with its pattern of expression and numerous potential isoforms, suggests a complex role for this molecule in cell interactions during neural development.
|Additional Information:||© 1992 Rockefeller University Press. Received for publication 28 January 1992 and in revised form 26 April 1992. We wish to thank Jennifer Kwang Hee Kim for excellent technical assistance on this project. Jon Faiz Kayyem was supported by a graduate fellowship from the Office of Naval Research (USA). Enrique J. de la Rosa was the recipient of postdoctoral fellowships of the Alexander von Humboldt-Stiftung (Germany) and Ministerio de Educacíon y Ciencia (Spain). This work was funded by institutional funding by Max-Planck-Gesellschaft, Lucille P. Markey Charitable Trust Grant in Developmental Biology to Caltech, and The National Institutes of Health (EY07752).|
|Official Citation:||Bravo/Nr-CAM is closely related to the cell adhesion molecules L1 and Ng-CAM and has a similar heterodimer structure J Cell Biol. 1992 September 1; 118(5): 1259–1270. PMCID: PMC2289593|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||29 Mar 2012 15:15|
|Last Modified:||26 Dec 2012 15:00|
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