Comparison of Plant Cytoplasmic Ribosomal Proteins by Two-Dimensional Polyacrylamide Gel Electrophoresis

Abstract

The electrophoretic mobilities of the cytoplasmic ribosomal proteins of several species of plants were compared using twodimensional electrophoresis. The total number of proteins as well as the number of acidic and basic proteins in individual species varied markedly. Of the species examined, Triticum aestivum had the highest number of basic cytoplasmic ribosomal proteins and Hordeum vulgare had less than half as many. However, marked similarities were noted in the electrophoretic mobilities of many of the proteins, especially for wheat, rye, and barley and for peas and beans. There was a statistically significant positive correlation between the numbers of basic proteins in the species and their chromosome number.It has been shown that the complex of ribosomal proteins prepared from various species of bacteria (8, 9), animals (3, 15), and higher plants (1,2,4,11,12,14) differ. Previous studies in our laboratory (5) employing two-dimensional electrophoresis to compare proteins of 70S and 80S wheat leaf ribosomes revealed that the proteins of chloroplast and cytoplasmic ribosomes differed in numbers, in their relative amounts, and in electrophoretic mobilities. The cytoplasmic ribosomes contained more proteins than have been reported for animals, and the chloroplast ribosomes contained more than have been reported for prokaryotes. Both classes of ribosomes contained a relatively large number of proteins that migrated towards the anode.In view of these findings, we set out to extend the work by comparing the ribosomal proteins of several species of higher plants. This report deals with the 80S cytoplasmic ribosomes of these species.MATERIALS AND METHODS Ribosomes from green leaves of different plant species were prepared by the method reported earlier (7). Leaves of 4.5-dayold seedlings of Triticum aestivum cv. Manitou, Triticum 'To whom reprint requests should be addressed. durum cv. Hercules, Hordeum vulgare cv. Gateway, Secale cereale cv. Prolific, and primary leaves of 10-day-old Phaseolus vulgaris cv. Black wax and Pisum sativum cv. Homesteader were used for isolation of the cytoplasmic ribosomes. Spinacia oleracea cv. Bloomsdale was supplied fresh by a local market gardener. For separation of 70S and 80S ribosomes from the same plant material in large quantities, a 7 to 35% (w/v) convex sucrose density gradient centrifugation was carried out in a Beckman Ti 14 zonal rotor (6). The Mg concentrations of the isolation media as well as of the zonal buffers were adjusted to provide optimal yield of ribosomes from the individual plant species. The concentrations were 1 mm for barley, 5 mM for beans, peas, and spinach, and 10 mm for rye and wheat.Proteins were extracted from the cytoplasmic ribosomes with 66% acetic acid in the presence of 30 mm MgClh. After lyophilization, the ribosomal proteins were dissolved in the electrophoresis buffer containing 6 M urea, and the protein concentration was determined by the method of Lowry et al. (10). For separation of the ribosomal proteins, the modified method of Ka...

Ribosomal Changes during Induction of Cold Hardiness in Black Locust Seedlings

“…The material remained frozen while being pulverized. The resulting powder was suspended in isolation buffer (50 mm tris-HCI, pH 8, 200 mm KCl, 25 mm MgCl2) with 10% (w/v) sucrose and stirred until warmed to 0 C. The suspension was squeezed through two layers of cheesecloth and centrifuged at 16,000g for 20 min. The resulting supernatant was filtered through one layer of Miracloth and Triton X-100 was added to 0.1% (w/v) with a small amount of Antifoam A (Sigma).…”

Plant cytoplasmic ribosomal proteins: an update on classification, nomenclature, evolution and resources

“…Plant RPs were first reported in 1960 (Setterfield et al., 1960). For much of the next 20 years, the principal focus was the isolation and characterization of plant RPs by using electrophoretic techniques; the proteins were numbered using integers as a function of their positions on gels (Götz & Arnold, 1980; Hanson et al., 1974; Nagabhushan et al., 1974; Vasconcelos & Bogorad, 1971). As different labs numbered the same protein with a different number, there was a strong need to develop a systematic nomenclature for RPs.…”