Poster: Late and Moved Abstracts

Abs # 1362: An 'integrin-like' protein in pea embryos is identified as lipoxygenase

Presenter:	Mo, Bing , bmo@usd.edu
Authors	Mo, Bing  (A)   Koster, Karen L (A)
Affiliations:	(A): University of South Dakota

An extracellular matrix-plasma membrane-cytoskeleton continuum may be a common feature for all eukaryotic cells, and several attempts have been made to identify proteins that can link these components together in plants. In animal cells, transmembrane proteins known as integrins mediate connections between the cytoskeleton and extracellular matrix, and immunologically related proteins have been detected in several plant species. We have reported the existence in pea embryos of a 100 kD protein that is 'integrin-like' in its antigenicity; it is recognized by the W1B10 antibody that was raised against the extracellular domain of the integrin b1 subunit. This protein is also ‘integrin-like’ in its localization at the cell surface in pea embryonic axes. However, database searching (BLAST) has not revealed any plant proteins with significant sequence homology to integrin proteins. Furthermore, screening of a cDNA library from developing pea seeds using degenerate probes for the W1B10 epitopes also found no significant homologous sequences. Using the anti-integrin W1B10 antibody, we have now successfully immunoprecipitated a 97 kD protein from pea embryos. We used mass spectrometry to identify this protein as pea seed lipoxygenase-3 (LOX-3), and we have confirmed this result by measuring lipoxygenase activity in the immunoprecipitate complex. LOX-3 and the integrin b1 subunit against which the W1B10 antibody was raised have no significant sequence homology, and we are currently investigating the reason for the strong antigenic similarity between these proteins.