Characterization of antibodies as probes for structural and biochemical studies of tektins from ciliary and flagellar microtubules

Abstract

Rabbit antibodies raised and purified against three tektins, proteins of flagellar doublet microtubules from sea-urchin sperm (Lytechinus pictus and Strongylocentrotus purpuratus), were used to study tektin biochemistry and their structural localization. Doublet microtubules were fractionated into tektin filaments and separated by SDS-PAGE into three major tektin polypeptide bands (Mr = 47, 51 and 55 (X 10(3)), which were used to immunize rabbits. Antibodies against each tektin (anti-tektins) were affinity-purified and then characterized by two-dimensional isoelectric focusing/SDS-PAGE immunoblotting and by immunofluorescence microscopy. In two-dimensional immunoblots of 0.5% Sarkosyl-resistant fractions of flagellar microtubules, the antibody against the 55 X 10(3) Mr tektin (anti-55) stained one major polypeptide of 55 X 10(3) Mr and pI 6.9, anti-51 stained two polypeptides of 51 X 10(3) Mr and pI approximately 6.15, and anti-47 stained one major polypeptide of 47 X 10(3) Mr and pI 6.15. The anti-tektins also stained several minor neighbouring polypeptides, which may be isoelectric variants, novel tektins or unrelated proteins. Furthermore, anti-47 crossreacted with the major 55 X 10(3) Mr polypeptide. By immunofluorescence microscopy all three anti-tektins stained methanol-fixed echinoderm sperm flagella and embryonic cilia. In addition, anti-47 and anti-55 stained unfixed, demembranated axonemes. Besides staining axonemes, all anti-tektins labelled the basal body region, and anti-51 labelled the sperm head envelope. These results indicate that the tektins are a complex family of proteins that are components of axonemal microtubules and possibly other cytoplasmic and nuclear structures.