Composition and properties of the sexual agglutinins of the flagellated green alga Chlamydomonas eugametos

Abstract

Sexual interaction between gametes of opposite mating type (mt) of the unicellular green alga Chlamydomonas eugametos starts with agglutination of the cells via particular glycoproteins on the flagellar surface. Purification of these socalled agglutinins was achieved by a three-step procedure consisting of, successively, gel filtration, anion-exchange chromatography, and high-performance gel filtration. The amino-acid and sugar compositions of both agglutinins showed a high degree of similarity; the most prominent amino acids were hydroxyproline, serine and glycine, and the main sugars were arabinose and galactose. The carbohydrate portions represented about half of the molecular mass of both agglutinins. Using high-performance gel filtration, a calibration curve was constructed for high-molecular-mass compounds from which the Stokes' radius of the sexual agglutinins could be estimated. The mt (+) agglutinin had a Stokes' radius of 39 nm and a sedimentation coefficient of 9.3 S. From these data its molecular mass was estimated to be 1.2·10(6). The corresponding data for the mt (-) agglutinin were 38 nm, 9.7 S and 1.3·10(6), respectively. The biological activity of both agglutinins was destroyed by mild periodate treatment. Treatment with specific glycosidases had a differential effect on the biological activity of the agglutinins. These observations indicate that carbohydrate side-chains are needed for biological activity and perhaps are responsible for the specifity of the sexual agglutinins. A comparison of both agglutinins is given and their possible structure is discussed in relation to their amino-acid and sugar compositions.

Domain conservation in several volvocalean cell wall proteins

“…Peak levels of W P 6 m R N A abundance correspond to the phase of the cell cycle after mitosis when new walls are being elaborated by the daughter cells. Although these results suggest that W P 6 is a structural c o m p o n e n t of the vegetative cell wall, new flagella are also being generated at this time of the cell cycle, and several flagellar H R G P s have been identified [ 6,40]. To test whether W P 6 is instead a flagellar protein, vegetative cells were subjected to p H shock, a procedure that removes flagella, initiates flagellar regeneration, Fig.…”

PlusandMinusSexual Agglutinins fromChlamydomonas reinhardtii

“…In pioneering studies, Wiese documented that the mating-typespecific components that induce mating-type plus gametic flagella to adhere to mating-type minus gametic flagella could be recovered from the culture medium (Fö rster and Wiese, 1954;Wiese, 1965). Subsequent analyses of such gamone preparations revealed them to contain flagellar membrane vesicles (Bergman et al, 1975;Snell, 1976;Musgrave et al, 1981), and further studies eventually led to the purification and extensive characterization of their component agglutinin proteins in both C. reinhardtii and the distantly related C. eugametos Cooper et al, 1983;Collin-Osdoby et al, 1984;Adair, 1985;Collin-Osdoby and Adair, 1985;Samson et al, 1987;Homan et al, 1988;Goodenough and Adair, 1989).…”

Characterization of the cell cycle in synchronous cultures of Chlamydomonas eugametos in relation to gametogenesis

“…To determine if an inactive form or precursor of the agglutinin might be present, the agglutinin was purified by HPLC gel-filtration of 2 M-GTC and 1 % SDS extracts (Musgrave et al, 1981;Samson et al, 1987). Fig.…”

“…Concentrated extracts of zoospores or gametes were analysed by gel filtration essentially as described by Musgrave et al (1981) and Samson et al (1987). Amicon concentrates were fractionated by HPLC gel filtration using a Bio-gel TSK 60 XL (Bio-Rad).…”