TABLE 1.

The PTS components and their various non-PTS interaction and/or phosphorylation partners

PTS component	Non-PTS phosphorylation/interaction partner(s)	Phosphorylation or interaction	Effect(s) of phosphorylation or interaction
EI (E. coli)	CheA, chemotaxis protein	Interaction	Stimulates CheA autophosphorylation
P∼EI (B. subtilis)	CheA, chemotaxis protein	Interaction	Inhibits CheA autophosphorylation
HPr (E. coli)	Glycogen phosphorylase	Interaction	Stimulates glycogen phosphorylase activity
P∼His-HPr (E. coli)	Glycogen phosphorylase	Interaction	Prevents binding of HPr to glycogen phosphorylase
P∼His-HPr	Antiterminators, BglG, SacY, LicT, etc.a	Phosphorylation in PRD2	Stimulates antitermination,b alternate CCR mechanism
	Transcription activators, LevR-like	Phosphorylation in the EIIAMan domain	Stimulates transcription, alternate CCR mechanism
	Transcription activators, MtlR-like	Phosphorylation in PRD2	Stimulates transcription, alternate CCR mechanism
	Transcription activators, LicR-like	Phosphorylation in PRD1 and PRD2	Stimulates transcription, alternate CCR mechanism
P∼His-HPr (firmicutes)	Glycerol kinase GlpK	Phosphorylation, His in the N-terminal half	Stimulates GlpK activity, inducer exclusion
	LacS, RafP; transporters for lactose, raffinose	Phosphorylation in the EIIAGlc domain	Stimulates substrate/galactose exchange
P-Ser-HPr (firmicutes)	CcpA	Interaction	CCR or CCA, catabolite corepressor
	Non-PTS transporters for maltose, ribose, etc.	Interaction	Inducer exclusionc
	RbsR	Interaction	Physiological role not yet established
P-Ser-Crh (bacilli)	CcpA	Interaction	CCR or CCA, catabolite corepressor
EIIAGlc (enterobacteria)	Non-PTS transporters LacY, MalK, MelB	Interaction	Inducer exclusion
	Glycerol kinase, GlpK	Interaction with the C-terminal domain	Inducer exclusion
	Fermentation respiration switch protein, FrsA	Interaction	Probably causes increased respiration
P∼EIIAGlc (enterobacteria)	Adenylate cyclase	Interaction	CCR, activation of adenylate cyclased
P∼EIIADha	DhaL, L subunit of dihydroxyacetone kinase	Phosphoryl transfer	ADP bound to DhaL is converted into ATP
EIIBGlc (enterobacteria)	Mlc	Interaction	Derepression of genes of the Mlc regulon
P∼EIIBs, Glc/Sac/Lac class	Antiterminators, BglG, SacY, LicT, etc.a	Phosphorylation in PRD1e	Inhibits antitermination, induction mechanism
P∼EIIBs, Man/Lac class	Transcription activators, LevR-like	Phosphorylation in PRD2e	Inhibits transcription, induction mechanism
P∼EIIBs, Mtl/Gut class	Transcription activators, MtlR-like	Phosphorylation in the EIIAMtl domaine	Inhibits transcription, induction mechanism
P∼EIIBs, Lac/Cel class	Transcription activators, LicR-like	Phosphorylation in the EIIAMtl domaine	Inhibits transcription, induction mechanism

^aFor a more detailed summary of well-studied antiterminators, see Table 4.

^bCertain antiterminators (such as SacY and GlcT of B. subtilis) are phosphorylated in vitro by P∼His-HPr in PRD2, but their activity is not stimulated by this modification.

^cAn interaction of P-Ser-HPr with the maltose or ribose transport systems in L. casei and L. lactis has so far not been demonstrated but is suggested from genetic experiments.

^dAn additional cellular factor seems to be necessary for the activation of adenylate cyclase by P∼EIIA^Glc (632).

^eIt is not clear whether phosphorylation of the antiterminators/transcription activators occurs via P∼His-HPr and P∼EIIBs stimulate only the phosphoryl transfer or whether the phosphoryl group is transferred from P∼EIIBs to the antiterminators/transcription activators. It is possible that both modes of regulation exist.