SALT-SOLUBLE SEED GLOBULINS OF VARIOUS DICOTYLEDONOUS AND MONOCOTYLEDONOUS PLANTS - I - ISOLATION PURIFICATION AND CHARACTERIZATION/

Detailed characterization of 21 purified seed globulins derived from b oth monocotyledonous and dicotyledonous plants indicated that globulin s from both class types (as well as within the same class type) lay wi thin a narrow molecular weight range between 300 000 and 370 000 Da an d were composed of multiple subunits. In all cases, purified globulins could be classified as hetero-oligomers being composed of a non-equim olar ratio of various subunits. The vast majority of subunits forming these globulins were shown to be held together by non-covalent bond fo rces. A small percentage of linkages between subunits were also shown to be disulfide linked, in the case of dicotyledonous seed globulins. It was also found that the majority of subunits composing the dicotyle donous and monocotyledonous seed globulins examined fell within two ve ry narrow molecular weight ranges, i.e. 20 000-27 000 and 30 000-39 00 0 Da and were believed to correspond to basic and acidic subunits, res pectively. Unlike monocotyledonous seed globulins, globulins derived f rom dicotyledonous plants were found to undergo alkaline-induced disso ciation due to electrostatic repulsion between subunits. The amino aci d composition of both dicotyledonous and monocotyledonous seed globuli ns suggests that they have a storage role and may be similar proteins based on a high content of amides (glutamic acids-glutamine and aspart ic acid-asparagine and arginine). From the results of the structural a nd chemical data obtained in this study, it is concluded that the 11S storage globulin, having several similar properties, exists in many le guminous and nonleguminous dicotyledonous plants as well as monocotyle donous plants. This similarity among 11S storage globulins could be du e either to convergent evolution in response to a common functional ne ed, or to common ancestry. (C) 1998 Elsevier Science Ltd. All rights r eserved.