8.A.8 The Phosphotransferase System HPr (HPr) Family
The HPr family consists of bacterial proteins, all of which function as phosphoryl transfer proteins. They are energy-coupling constituents of the phosphotransferase system (PTS) (TC #4.A.1-4.A.7) which catalyzes sugar uptake via a group translocation mechanism. HPr proteins are not known to be homologous to any non-PTS proteins. The E. coli genome encodes five HPr paralogues. The functions of several of these proteins are known. They function in PTS-related regulatory capacities.
HPr of the PTS (Araki et al., 2011)
HPr of Rhodococcus jostii (Q0S1N3)
PTS phosphocarrier protein, HPr (based on homology)
HPr of Haloterrigena turkmenica (D2RXA6)
Phosphocarrier Protein, HPr. (functions with 4.A.2.1.15; Pickl et al., 2012).
HPr of Haloferax volcanii (D4GYE3)
Phosphotransferase system, phosphocarrier protein HPr of 89 aas. This protein is encoded in the same operon with an Enzyme I (TC# 8.A.7.1.5) and the IIC and IID genes of a mannose-type PTS system (TC# 4.A.6.1.20).
HPr of Caldithrix abyssi
HPr of an archaeal PTS of the mannose (Man) type; 90 aas.
HPr of Thermofilum pendens
The phosphocarrierprotein of the PTS, HPr (PtsH) of 93 aas. In this organism and another Streptomyces species, S. lividans, HPr and Enzyme I are inducible by fructose (Titgemeyer et al. 1995), and they comprise a complete fructose phosphorylation and transport system (Parche et al. 1999). All pts related genes present in the S. coelicolor genome have been identifed, and in addition to the Fructose PTS described above, there are several other PTS enzyme II complexes, that transport other sugars (Parche et al. 1999) including N-acetylglucosamine which serves as a sensing device as well as a transporter/kinase for N-acetylglucosamine (see TC# 4.A.1.1.20) (Nothaft et al. 2010).
HPr of Streptomyces coelicolor