Phosphoenolpyruvate-dependent mannitol phosphotransferase system of Escherichia coli: overexpression, purification, and characterization of the enzymatically active C-terminal domain of enzyme IImtl equivalent to enzyme IIImtl.
The extreme C-terminus (Ser-490 to Lys-637) of the Escherichia coli EIImtl was subcloned to test structural and mechanistic proposals about the existence of an EIII-like domain in this enzyme. Oligonucleotide-directed mutagenesis was used to produce a unique NcoI restriction site and, at the same time, to change Ser-490 into methionine in a flexible region in front of the proposed EIII-like domain. The 16-kDa C-terminal domain (CI) was overexpressed in Escherichia coli, purified, and analyzed in vitro for catalytic activity in the presence of an EIImtl mutated at its first phosphorylation site, His-554 (EII-H554A). The results presented show that this domain can be expressed as a structurally stable, enzymatically active entity which is able to restore the PEP-dependent phosphorylation activity of the mutant EIImtl-H554A to 25% of wild-type levels. To demonstrate the EIII activity of the CI domain in a more direct way, we also substituted it for EIIImtl in the Staphylococcus carnosus system. The CI domain was active in transferring the phosphoryl group to Staph. carnosus EII; however, it was 6.5 times less active compared to Staph. carnosus EIIImtl itself. EIIImtl from Staph. carnosus, on the other hand, was able to substitute for the isolated C-terminal domain in the E. coli mannitol phosphorylation assay; however, it appeared to be 2 or 3 times less effective.
van Weeghel
R P
RP
Department of Physical Chemistry, Institute BIOSON, Groningen, The Netherlands.
Meyer
G H
GH
Keck
W
W
Robillard
G T
GT
D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D016297:Mutagenesis, Site-Directed; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids; D015183:Restriction Mapping; D013210:Staphylococcus / Q000201:enzymology / Q000235:genetics
D029968:Escherichia coli Proteins; D009004:Monosaccharide Transport Proteins; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C022358:mannitol PTS permease, E coli; C061852:phosphoenolpyruvate-mannitol-specific enzyme III