Kittur, Farooqahmed S. , Yu, Hyun Young , Bevan, David R. , Esen, Asim .
Maize beta-Glucosidase Aggregating Factor (BGAF) Homolog from Sorghum is a Mannose-specific Chimeric Lectin.
Lectins are proteins that bind specifically and reversibly to carbohydrates, resulting in cell agglutination or precipitation of glycoconjugates. Recently, we have identified beta-glucosidase aggregating factor (BGAF) from maize as a polyspecific jacalin-related chimeric lectin and showed that its lectin domain is responsible for beta-glucosidase aggregation (Kittur et al, J. Biol. Chem. (2007), 282, 7299-7311). A pfam database search revealed that there are at least 12 BGAF-like proteins and they all come from family gramineae. Interestingly, maize BGAF is the only protein for which an activity (beta-glucosidase aggregation and lectin activity) has been described. Information on sugar specificities of other members of this class of chimeric lectins is lacking and it is not known whether other members of this class are involved in protein-protein interactions. We identified an EST clone from sorghum and determined its complete cDNA sequence. The deduced amino acid sequence showed 67% identity with maize BGAF and the protein revealed same modular structure as maize BGAF. To answer above questions, we isolated native protein from sorghum coleoptile and produced its recombinant version in Escherichia coli. The native and recombinant proteins were 32 kD monomers. Both proteins agglutinated rabbit erythrocytes, and their hemagglutinating activity was inhibited by mannose and mannose-containing glycoproteins. Pull-down and gel-shift assays showed no evidence of binding to sorghum or maize beta-glucosidases. Attempts to trap binding partners using immobilized lectin were unsuccessful. These results suggests that the beta-glucosidase binding and aggregation activity is unique to maize BGAF and that the other members may not have protein aggregation activity.
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1 - Virginia Polytechnic Institute and State University, Biological Sciences, 5028 Derring Hall, Blacksburg, Virginia, 24061, USA
2 - Virginia Polytechnic Institute and State University, Biological Sciences
3 - Virginia Polytechnic Institute and State University, Biochemistry
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM