CLONING OF A PEA CDNA-ENCODING A POLYPEPTIDE OF THE LIGHT-HARVESTING COMPLEX-ASSOCIATED WITH PHOTOSYSTEM-I USING A MONOCLONAL-ANTIBODY

A monoclonal antibody (MAb UB42) is described that binds to thylakoids in pea chloroplasts, as shown by EM-immunogold labelling. The antibod y recognised proteins of ca. 23-29 kDa in western blots of a pea leaf homogenate. A cDNA library was prepared from pea epidermal cells in th e vector lambda ZAP II, and immunoscreening of the library with UB42 l ed to the isolation of a clone, pUB42. This was sequenced and had an o pen reading frame of 269 codons encoding a predicted polypeptide of 28 .9 kDa. The sequence showed extensive homology with three closely rela ted polypeptides belonging to a family of chlorophyll a/b-binding prot eins from the light harvesting complex of photosytem I (LHCI). Collect ively, the results suggest that MAb UB42 recognises an epitope on the type II chlorophyll a/b-binding protein from LHCI and that clone pUB42 encodes this protein.