HIGH-MOLECULAR-WEIGHT POLYPEPTIDES RELATED TO DYNEIN HEAVY-CHAINS IN NICOTIANA-TABACUM POLLEN TUBES

Nicotiana tabacum pollen tubes contain two high molecular weight polyp eptides (about 400 kDa), which are specifically expressed during polle n germination and pollen tube growth in BK medium, The high molecular weight doublet resembles the dynein heavy chains in some biochemical p roperties, Sedimentation profiles of pollen tube extracts show that th e high molecular weight bands have sedimentation coefficients of 22 S and 12 S, respectively, ATPase assay of sedimentation fractions shows an activity ten times higher when stimulated by the presence of bovine brain microtubules in fractions containing the 22 S high molecular we ight polypeptide. Both these high molecular weight polypeptides can bi nd microtubules in an ATP-dependent fashion, A mouse antiserum to a sy nthetic peptide reproducing the sequence of the most conserved ATP-bin ding site among dynein heavy chains recognized the two high molecular weight polypeptides. Therefore these polypeptides have sequences immun ologically related to the ATP binding sites of dynein heavy chains.