Characterisation and Subunit Structures of the Vicilin Storage Proteins of Pea (Pisum sativum L.)

Abstract

Investigations of the vicilin fraction of the storage proteins of pea (Pisum sativum L.) have shown that its major components are a number of protein species of M , 170000. Convicilin ( M , 280000, composed of 71 000-M, subunits) is a separable component of this fraction. The vicilin proteins are composed principally of z 50000-M, polypeptides, but also contain a number of smaller polypeptides. The sub-unit polypeptide composition of vicilin changes during seed development quantitatively and qualitatively. Vicilin sub-units have been shown to be synthesised as polypeptides of M , z 50000 by means of pulse-labelling experiments in vivo, and synthesis of vicilin in vitro directed by mRNA, polysomes and microsomes extracted from pea cotyledons in cell-free translation systems. Polypeptides then undergo two distinct types of proteolytic modification : (a) co-translational removal of a small polypeptide ( M , less than 1000); (b) 'nicking' of polypeptide chains in assembled vicilin molecules, which occurs more than 4 h after their initial synthesis. The basic structure of the vicilin molecule is thus a multimer, possibly a trimer, of z 50000-M, subunits. The heterogeneity of the initially synthesised SOOOO-M, subunits accounts not only for the several different SOOOO-M, polypeptides found in vicilin, but also for the range of minor polypeptides, since the 'nicking' points will differ among subunits. It also accounts for the observed partial separation of vicilin into different molecular species, since different subunit combinations will give rise to molecules with different properties. Vicilin is also glycosylated and this is a source of further variation.The storage proteins of pea (Pisum sativum L.) have been conventionally divided into two fractions, legumin and vicilin [l]. Depending on the variety, vicilin is usually the quantitatively smaller fraction and is thought to contain more than one protein [2], since it is heterogeneous when analysed in the ultracentrifuge [3] by ion-exchange chromatography [4] or when fractionated by solubility under varying conditions of pH, ionic strength and temperature [5,6] or by carbohydrate affinity chromatography [7]. The vicilin fraction contains major polypeptides of M ,

Sequestration of Pea Reserve Proteins by Rough Microsomes

“…This polypeptide may be the precursor for legumin that has been previously described (13,30). The failure to immunoprecipitate legumin and vicilin polypeptides from in vitro translation products that exactly correspond to polypeptides found in vivo has been reported in other studies (13,14,(16)(17)(18). Sequestration of Proteins Synthesized In Vitro.…”

Biosynthesis of Storage Proteins in Ripening Agrostemma githago L. Seeds

“…In peas the lower mol wt vicilin subunits are also derived from large precursor proteins. After the successive cleavage events, the subunits are not linked by disulfide bridges (9,16). A similar splitting of high mol wt precursors is also reported for other species, but no test was made for the presence of disulfide bridges (15,29).…”

A comparison of interfacial behaviours of pea (Pisum sativum L.) legumin and vicilin at air/water interface

“…Die Isotherme I C~ = f(log c) zeigte, daD die zur Erreichung dsr Plateau-Werte von ire erforderlichen Konzentrationen etwa 11, 7 . Beim Studium der Oberflacheneigenschaften von ViciliniLegumin-Mischungen wurde beobachtet, daB…”