Trypanosoma brucei:Identification of an Internal Region of Phosphoglycerate Kinase Required for Targeting to Glycosomal Microbodies

Abstract

Among the microbodies found in eukaryotes are the glycosomes ofTrypanosoma brucei,thought to be closely related to peroxisomes. Two types of targeting signals for glycosomes have been identified thus far: type 1 at the C-terminus and type 2 at the N-terminus. In this report, we use an epitope-tagging system to characterize the targeting signal found on the minor glycosomal isozyme of phosphoglycerate kinase, 56PGK. No type 1 or 2 signal was found; rather, the topogenic information was found to be internal. Chimeric molecules formed with the cytoplasmic phosphoglycerate kinase isozyme indicate that a region between amino acids 24 and 91 of 56PGK is essential for glycosomal targeting. No homology was found between this region and peroxisomal proteins containing internal targeting signals.