The activities of the Escherichia coli MalK protein in maltose transport, regulation, and inducer exclusion can be separated by mutations

Abstract

The maltose regulon consists of several genes encoding proteins involved in the uptake and utilization of maltose

Involvement of the C-terminal Domain of an ATP-binding Subunit in the Regulation of the ABC-type Nitrate/Nitrite Transporter of the Cyanobacterium Synechococcus sp. Strain PCC 7942

“…On the other hand, the similarity of the C-terminal domain of NrtC in amino acid sequence to NrtA (5), which has been shown to be a nitrate/nitrite-binding protein (18), suggests that the C-terminal domain of NrtC may be an effector-binding domain. Because the maltose transporter of E. coli is inhibited by a proteinaceous effector binding to the C-terminal extension of its ATP-binding subunit (37,38), the regulation of the cyanobacterial nitrate transporter might also involve a proteinaceous effector. Genetic and biochemical studies are being performed to clarify the molecular mechanism of the regulation of nitrate/nitrite transport by the Cterminal domain of the ATP-binding subunit.…”

Secondary solute transport in bacteria

“…Mutations have been isolated that render LacY of E. coli [326,327], MelB of S. typhimurium [322], and MalK of E. coli [323,328] resistant to inducer exclusion, i.e., to inhibiton by PTS sugars. These mutations correspond to T7I, MllI, A198V and $209I in LacY (Fig.…”

“…8B, open arrow), suggesting that, in addition to the carboxy terminus, also the large cytoplasmic loop between a-helices VI and VII interacts with IIA. Finally, sequence homology between the central loop of LacY and part of MalK, containing mutations that lead to resistance to PTS sugars, has been detected [328].…”

Disulfide Cross-linking Reveals a Site of Stable Interaction between C-terminal Regulatory Domains of the Two MalK Subunits in the Maltose Transport Complex

“…Evidence of a direct protein-protein interaction between isolated MalK and MalT has been presented (17). IIA glc , an enzyme participating in the transport and phosphorylation of glucose, also appears to bind directly to MalK, inhibiting maltose transport when glucose is present by a mechanism known as inducer exclusion (15,20,21).…”

“…One domain is predominantly ␤-sheet and forms a classic nucleotide-binding fold as observed in the F 1 -ATPase (14), and the second domain is ␣-helical and is specific to ABC transporters. The MalK protein differs in that it contains a third domain at its C terminus that is involved in regulatory functions, as deduced from mutational analysis (15,16). MalK binds MalT, a positive transcription factor that is required for expression of the genes involved in maltose transport and metabolism (17).…”