Characterization of the Calcium-Binding Contractile Protein Centrin from Tetraselmis striata (Pleurastrophyceae)

ABSTRACT. Centrin is a major protein of the contactile striated flagellar roots of the green alga Tetraselmis striata . We present a newly modified procedure for the preparation of centrin in sufficient quantity and purity to allow for detailed biochemical characterization. We establish that centrin purified by differential solubility, followed by phenyl-Sepharose and DEAE-Sephacel chromatography is identical with the protein extracted directly from striated flagellar roots with regard to molecular weight, isoelectric point, and calcium-dependent behavior in SDS-PAGE. We also compare the biochemical properties of purified centrin with calmodulin isolated from Tetraselmis and calmodulin isolated from mammalian brain. Centrin can be fully distinguished from either algal or mammalian calmodulin on the basis of molecular weight, isoelectric point, calcium-dependent behavior in SDS-PAGE, proteolytic peptide maps, amino acid composition, ability to activate bovine brain phosphodiesterase, and reactivity with specific antibodies.     

Molecular and Subunit Heterogeneity of Legumin of Pisum sativum L. (Garden Pea)-- A Multi-Dimensional Gel Electrophoretic Study

Pisum sativum legumin has been shown to be heterogeneous withrespect to the existence of different molecular forms, the molecularweights of subunit pairs, and the molecular weights and isoelectricpoints of constituent subunits. Disulphide-bonded subunit pairswith mol. wt. 54 000 constitute a major part of total legumin.In addition, subunit pairs varying in mol. wt. from 35 000 to58 000 have been observed which associate in various ways togive rise to at least three distinct molecular forms of leguminseparable on non-dissociating gels. ‘Three-dimensional’gel electro-phoresis has been employed to understand the consitutionof these forms in detail.     

Electrical Events Correlated with Contractile Vacuole Activity in the Suctorian, Heliophrya

SYNOPSIS. The surface membrane potentials of suctorian genus Heliophrya were studied with intracellular electrodes. Resting membrane potentials averaged -32 mV, and spontaneous depolarizing potentials occurring at apparently random intervals and having a variety of waveforms were routinely observed. Such spontaneous potentials were correlated in time with visually monitored contractile vacuole activity. Individual contractile vacuoles had unique, although somewhat variable, electrical signatures. In the presence of an intracellular electrode all vacuoles contracted independently, but at approximately the same frequency. The amplitude of the electrical potentials increased when the membrane was hyperpolarized and decreased when it was depolarized. The sign of such potentials reversed at between -10 mV and the zero membrane potential. A 20% decrease in the membrane resistance was measured at the peak of the spontaneous depolarizing potentials.     

Fatty Acid and Chlorophyll Levels of Coastal Bermudagrass during the Day and during Maturation

Lipids were extracted from fresh, field-grown coastal bermudagrass (Cynodon dactylon (L.) Pers.) and the fatty acids determined by gas chromatography. Total fatty acid levels (dry weight basis) increased during the day and reached a single maximum at sunset in 2-week-old grass; whereas, in older grass, the fluctuations in fatty acid levels showed two maxima. The first maximum occurred 4 h after sunrise and the second maximum occurred at sunset. Total fatty acid levels, based on dry weight, decreased during the first 6 weeks of growth and changed very little after an additional 4 weeks' growth in bermudagrass leaf blades. Chlorophyll levels (dry weight basis) continuously decreased during the entire growth period (10 weeks). Chlorophyll alb ratios increased at sunset in 2- and 6-week-old grass, but this ratio did not change during the day in subsequent growth stages. The results of these experiments show that stages of maturity affected fatty acid fluctuations during the day as well as total fatty acid and chlorophyll levels in Coastal bermudagrass leaf blades. Chlorophyll alb ratios varied independently of fatty acid levels.