3 GENES AND 2 ISOZYMES - GENE CONVERSION AND THE COMPARTMENTALIZATIONAND EXPRESSION OF THE PHOSPHOGLYCERATE KINASES OF TRYPANOSOMA (NANNOMONAS) CONGOLENSE

The glycosome, a microbody organelle found only in kinetoplastid proto zoa, compartmentalizes the first six enzymes of glycolysis. In order t o better understand the regulation and targeting of glycolytic enzymes in trypanosomes, we have cloned and analyzed the three genes of the p hosphoglycerate kinase (PGK) complex of Trypanosoma (Nannomonas) congo lense. The organization of the genes within the complex is similar to that of Trypanosoma brucei brucei. The nucleotide and amino-acid seque nces, including those of the novel high-molecular-weight 56PGK, show s ubstantial cross-species similarity. However, the two downstream genes , c1PGK and c2PGK, encode identical isozymes in T. congolense, while t hey encode distinct glycosomal and cytoplasmic isozymes in T. brucei. Western analysis also indicated that there are only two isozymes in T. congolense and that these are constitutively expressed. Differential digitonin solubilization of the trypanosomes indicated that 56PGK is p rimarily localized to the glycosome, as expected, and that c1/c2PGK is cytoplasmic. Northern analysis demonstrates that while 56PGK is const itutively expressed, c2PGK and c2PGK mRNAs are differentially expresse d in the T. congolense developmental stages. This work demonstrates th at T. congolense has only one PGK isozyme, 56PGK, that is predominantl y localized in glycosomes.