Structural analysis of a plant sucrose carrier using monoclonal antibodiesand bacteriophage lambda surface display

Monoclonal antibodies mere raised and selected against recombinant Plantago major PmSUC2 sucrose carrier protein, Epitopes of two monoclonal antibodie s (PS2-1A2 and PS2-4D4) were mapped using N-terminally truncated PmSUC2 pro teins and a lambda library displaying random PmSUC2 peptides, PS2-1A2 recog nizes an octapeptide close to the N-terminus of PmSUC2, PS2-4D4 binds to a decapeptide at the very C-terminus, Analyses of antibody binding to yeast p rotoplasts with functionally active, tagged PmSUC2 protein revealed that bo th epitopes are located in cytoplasmic domains of PmSUC2, These results sup port a model for plant sucrose transporters containing 12 transmembrane hel ices with the N-terminus and the C-terminus on the cytoplasmic side of the plasma membrane. (C) 1999 Federation of European Biochemical Societies.