POSTTRANSLATIONAL MODIFICATIONS OF ALPHA-TUBULIN AND BETA-TUBULIN IN GIARDIA-LAMBLIA, AN ANCIENT EUKARYOTE

Tubulin of Giardia lamblia, a representative of the oldest eukaryotes, was screened for posttranslational modifications, Mass spectrometry o f the carboxy-terminal peptides documents a large number of variants, Both alpha-and beta-tubulin show polyglycylation with up to 20 and 15 extra glycyl residues respectively. Minor variants show a low level of glutamylation without or with glycylation. The glutamylation-specific antibody GT335 detects alpha- and beta-tubulin in immunoblots, The te rminal tyrosine is fully retained in alpha-tubulin, which is completel y acetylated at Lys-40, Thus except for the detyrosinationl/tyrosinati on cycle all posttranslational modifications known for higher eukaryot es are already present in Giardia. (C) 1997 Federation of European Bio chemical Societies.