Fructose transport and degradation in Haloarchaea
In most bacteria fructose uptake is mediated by a phosphoenolpyruvate (PEP) dependent phosphotransferase system (PTS), which phosphorylates fructose during transport to fructose-1-phosphate. In general, PTS are composed of five components, two cytoplasmic proteins, protein kinase enzyme I (EI) and histidine protein (HPr), and the substrate-specific enzyme II (EII). EII consists of two soluble components (EIIA and EIIB) and a transmembrane component (EIIC) that carries out both the transport and concomitant phosphorylation of the substrate across the membrane. The transfer of the phosphoryl group from PEP to sugar proceeds via the transient phosphorylation of EI, HPr, EIIA, and EIIB. So far, PTS-like sugar uptake systems have not been reported in the archaeal domain.
Our studies indicate that fructose uptake and degradation in the haloarchaeon Haloferax volcanii involve a bacterial type PTS, forming fructose-1-phosphate, a specific fructose-1-phosphate kinase (1-PFK) and a metal dependent class II fructose-1,6-bisphosphate aldolase (FBA). The studies included transcriptional analyses, construction and analyses of knock-out mutants and expression and characterization of enzymes involved. This is the first report of the functional involvement of a bacterial type PTS in sugar transport in archaea. The high similarity of bacterial and haloarchaeal PTS and the absence of PTS in all other archaea and eukarya indicate lateral gene transfer of PTS from bacteria to the haloarchaea.
Pickl et al. (2012) Fructose degradation in the haloarchaeon Haloferax volcanii involves a bacterial phosphoenolpyruvate dependent phosphotransferase system, fructose-1-phosphate kinase, and class II fructose-1,6-bisphosphate aldolase. J Bacteriol 194:3088-97