UBIQUITINATION AND ATP LEVELS IN GARDEN PEA-SEEDS

Developing and germinating pea seeds contain high levels of ubiquitin conjugated to proteins as detected on western blots. In contrast, the level of dry seed protein-ubiquitin conjugates in vivo appears low, wi th mainly free ubiquitin present. The ubiquitination of endogenous dry pea seed proteins is observed in vitro, relying only on already prese nt endogenous ubiquitin, suggesting the enzymatic machinery for ubiqui tination is present in the dry seed. Energy source in the form of ATP increased the formation of large molecular mass conjugates, although s ome conjugation took place without added ATP The usefulness of dry see ds, having low levels of ATP which can then be manipulated in the in v itro reaction is discussed. ATP and ubiquitin degrading activities are detected in the crude in vitro system, pointing to the need to purify the individual components, or to seek specific inhibitors of the unde sirable secondary reactions.