THE SEXUAL AGGLUTININS IN CHLAMYDOMONAS-EUGAMETOS ARE SULFATED GLYCOPROTEINS

Sexual adhesion in the green alga Chlamydomonas eugametos is mediated by hydroxyproline-containing glycoproteins (agglutinins). The agglutin ins were metabolically labelled with [S-35]sulphate. The sulphur-conta ining amino acids methionine and cysteine were not detectably labelled ; tittle or no sulphated tyrosine was detected. This indicated that th e radioactive label had been largely or exclusively incorporated into sulphated sugar residues. Acid hydrolysis released essentially all rad ioactivity as free sulphate. Short periods of hydrolysis released sulp hated oligosaccharides. Beta-Elimination released about 20-25% of the sulphated saccharides, indicating that these are O-linked to serine or threonine or both. The remaining sulphated sugar chains are presumabl y O-linked to hydroxyproline. It is proposed that the sulphated sugars of the agglutinins play a role in sexual adhesion.