In search of molecular dovetails in mussel byssus: From the threads to thestem

We recently described the cDNA sequence for a unique collagenous protein, p reCol-P, in the byssal threads of the marine mussel Mytilus edulis. The tra nslated amino acid sequence encodes an unprecedented block-copolymer-like s equence with a central collagenous domain flanked by elastin-like sequences . Were, we report on the presence of two additional variants of preCol-P. T he distribution of these variants in M. edulis foot tissue was examined by reverse transcription followed by polymerase chain reaction (RT-PCR) and in situ hybridization techniques. One of the variants, P33, exhibits a graded distribution with decreasing concentrations along the longitudinal axis of the foot, The second variant, P22, is expressed only at the base of the mu ssel's foot. In situ hybridization confirms the exclusive expression of pre Col-P variant P22 in the stem gland. We propose that this variant may repre sent a molecular 'dovetail' between the proximal thread and the byssal stem , imparting extensibility and elastic recoil to the ring portion of the ste m.