In bean [Phaseolus vulgaris L.) seeds, the ?-amylase inhibitor (?AI) is a major lectin-related protein. We describe here its synthesis and accumulation in the protein storage vacuole (PSV) of cotyledonary cells of the developing seed. ?-Amylase inhibitor is synthesized on the endoplasmic reticulum where it is glycosylated to yield two major glycoforms. In common with other vacuolar seed proteins. ?Al is transported to the PSV along the secretory pathway. via Golgi-derived vesicles. In the Golgi complex, some of the oligosaccliaride side chains are modified. The precursor is then transported into the PSV, where the final maturation occurs in two steps. Firstly a few amino acids are removed from the C terminus, then the polypeptide is cleaved endoproteolytically to give the mature ?Al form, consisting of 5 major polypeptides in the M1 range of 15000-20000. The absence of oligosaccharide side chains or their presence in the unmodified form appear to be unrelated to either intracellular transport and maturation of ?A1 in the PSV.
The alpha-amylase inhibitor of bean seed: two-step proteolytic maturation in the protein storage vacuoles of the developing cotyledon.
Santino A;Daminati MG;Vitale A;Bollini R
1992
Abstract
In bean [Phaseolus vulgaris L.) seeds, the ?-amylase inhibitor (?AI) is a major lectin-related protein. We describe here its synthesis and accumulation in the protein storage vacuole (PSV) of cotyledonary cells of the developing seed. ?-Amylase inhibitor is synthesized on the endoplasmic reticulum where it is glycosylated to yield two major glycoforms. In common with other vacuolar seed proteins. ?Al is transported to the PSV along the secretory pathway. via Golgi-derived vesicles. In the Golgi complex, some of the oligosaccliaride side chains are modified. The precursor is then transported into the PSV, where the final maturation occurs in two steps. Firstly a few amino acids are removed from the C terminus, then the polypeptide is cleaved endoproteolytically to give the mature ?Al form, consisting of 5 major polypeptides in the M1 range of 15000-20000. The absence of oligosaccharide side chains or their presence in the unmodified form appear to be unrelated to either intracellular transport and maturation of ?A1 in the PSV.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
