The hyperthermophilic bacterium Thermotoga neapolitana possesses two isozymes of the 3-phosphoglycerate kinase/triosephosphate isomerase fusion protein

Abstract

The phosphoglycerate kinase ( pgk), triosephosphate isomerase ( tpi), and enolase ( eno) genes from Thermotoga neapolitana have been cloned and expressed in Escherichia coli. In high copy number, the pgk gene complemented an E. coli pgk − strain. In T. neapolitana, the pgk and tpi genes appear to be fused and eno is near those genes. Like T. maritima, T. neapolitana produces phosphoglycerate kinase as both an individual enzyme and a fusion protein with triosephosphate isomerase, and triosephosphate isomerase activity is not found without associated phosphoglycerate kinase activity. Unlike T. maritima, which forms only a 70-kDa fusion protein, T. neapolitana expresses both 73-kDa and 81-kDa isozymes of this fusion protein. These isozymes are present in both T. neapolitana cells and in E. coli cells expressing T. neapolitana genes.