Abstract
The structure of the gene encoding a chicken liver receptor, the chicken hepatic lectin, which mediates endocytosis of glycoproteins has been established. The coding sequence is divided into six exons separated by five introns. The first three exons correspond to separate functional domains of the receptor polypeptide (cytoplasmic tail, transmembrane sequence, and extracellular neck region), while the final three exons encode the Ca(2+)-dependent carbohydrate-recognition domain. These results, as well as computer-assisted multiple sequence comparisons, establish this receptor as the evolutionary homolog of the mammalian asialoglycoprotein receptors. It is interesting that the chicken receptor falls into a subfamily of proteins along with the mammalian asialoglycoprotein receptors, since the saccharide-binding specificity of the chicken receptor resembles more closely that of a different set of calcium-dependent animal lectins, which includes the mannose-binding proteins. The portions of the genes encoding the carbohydrate-recognition domains of these proteins lack introns. The results suggest that divergence of intron-containing and intron-lacking carbohydrate-recognition domains preceded shuffling events in which other functional domains were associated with the carbohydrate-recognition domains. This was followed by further divergence, generating a variety of saccharide-binding specificities.
Highlights
The structure of the gene encoding a chicken liver receptor, the chicken hepatic lectin, which mediates endocytosis of glycoproteins has been established
Structural analysis of two homologous forms of these proteins reveals that the COOH-terminal portion of each constitutes a CRD homologous with the CRDs of the membrane lectins [8].Much of the remainder of each mannosebinding protein consists of collagen-like sequences
Animal lectins can be classified based on amino acid sequence similarities as well as otherproperties
Summary
0 1991 hy The American Society for Biochemistry and Molecular Biology, Inc. Vol 266, No 18, Issue of June 25, pp. 11604-11609.1991 Printed in U.S.A. Similar flanking domains, it canbe suggested that each group arose by divergence from a single ancestral gene containing a cartilage proteoglycan core protein are in similar locations, CRD-coding region joined to exons encoding precursors to the correspondence is not asprecise. This indicates that there these additional domains. Sequence similarity is notapparent which the genomic structure hasbeen analyzed, the segments when the cytoplasmic tails ormembrane anchors of CHL are of the proteinscompared were restricted to those correspond- compared with the corresponding portions of the mammalian ing to the one or three exons encoding the CRDs. In each asialoglycoprotein receptors by varions algorithms. For exam- descend from a common CRD-encoding precursor which beple, all of the CRDs associated with collagenous domains came duplicated prior to theshuffling events which generated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
