Table 1.

mal genes and their products, genes controlling mal gene expression, and genes related to maltodextrin metabolism

GenePosition on chromosome (min)Gene product and functionReference(s)
mal genes and their main regulator
malT76.5Transcriptional activator, essential for transcription of all mal genes except the malI/X/Y gene cluster. Binds ATP and maltotriose as inducer.34, 40, 66, 206, 214, 215, 280
 malE91.4Periplasmic MBP; binds maltose/maltodextrins with micromolar affinity.37, 76, 107-109, 128, 138, 244, 248, 257, 264, 265
 malF91.4Intrinsic membrane protein of the transport system. In association with MalG and MalK, it forms the MalFGK2 translocation complex.41, 80, 82, 93, 252, 273
 malG91.4Intrinsic membrane protein of the transport system. In association with MalF and MalK, it forms the MalFGK2 translocation complex.25, 50-52, 254, 273
 malK91.5Transport ATPase, responsible for energization of transport. In association with MalF and MalG, it forms the MalFGK2 translocation complex. Target of inducer exclusion by unphosphorylated EIIAGlc of the PTS. In the absence of inducer, it interacts with MalT to cause repression.7, 44, 53, 55, 60, 103, 115, 147, 151, 166, 167, 184, 210, 251
 lamB91.5Receptor for phage λ and specific pore for maltodextrins (maltoporin, glycoporin).16, 39, 85, 92, 124, 136, 207, 231, 263, 265
 malM91.5Periplasmic protein of unknown function, partially associated with the outer membrane. Contains an Ala-Pro linker also found in OmpA.104, 222, 234
 malP76.5Maltodextrin phosphorylase. Substrates are maltopentaose and larger maltooligosaccharides.malP mutants still grow on maltose but accumulate large amount of maltodextrins under these conditions.177, 181, 229, 242, 290
 malQ76.4Amylomaltase. Maltodextrinyltransferase with maltotriose as the smallest substrate.malQ mutants cannot grow on maltose, are sensitive to maltose, and are constitutive for mal gene expression.69, 165, 182, 194, 294, 295
 malS80.5Periplasmic α-amylase, cleaves preferentially maltohexaose from the nonreducing end of meltotextrins.91, 92, 235, 256
 malZ9.1Maltodextrin glucosidase and γ-cyclodextrinase, cleaves glucose sequentially from the reducing end of maltodextrins. Maltotriose is the smallest substrate. It linearizes γ-cyclodextrin but not α- and β-cyclodextrin.185, 211, 267
Genes whose products controlmal gene expression
 cya85.9Adenylate cyclase. Production of cAMP, involvement in catabolite repression.75, 134, 187
 crp75.1cAMP-binding protein, needed for the transcription of malT and the transport gene cluster.35, 135, 143, 206
 malI36.6Repressor for malXY, not dependent on MalT, inducer unknown.209
 malX36.6Enzyme II of the PTS, transports and phosphorylates glucose, can transport maltose by diffusion.208
 malY36.6βC-S lyase (cystathionase). Overproduction reduces mal gene expression by interaction with MalT and its inactivation.208, 301
 aes (ybaC,orf203)10.8Esterase. Overproduction reducesmal gene expression, presumably by interaction with MalT and its inactivation.164, 186
 mlc35.9Gene regulator, represses the expression of malT and manXYZ.70, 131
 maa (mac, F183a)10.32Glucose/maltose transacetylase, not MalT dependent, responsible for exit of maltose and glucose in their acetylated forms.20, 26
Genes whose products affect endogenous synthesis of inducer
 glgA75.4Glycogen synthase. ADP-dependent synthesis of glycogen. Degradation of glycogen yields maltotriose, which, in malQ mutants, leads to constitutivity of the maltose system. glgA mutants have a lower level on uninduced mal gene expression thanglgA+ strains.148, 176
 glgC75.4ADP-glucose-pyrophosphorylase. Synthesis of ADP-glucose, needed for constitutive mal gene expression in malQ mutants. glgC mutants have a lower uninduced mal gene expression thanglgC+ strains.4, 176
 glgP75.4Glycogen phosphorylase. Glycogen degradation and formation of glucose-1-phosphate. Possibly involved in synthesis of endogenous inducer.300
 glgB75.4Branching enzyme5, 176
 glgX75.4Amylase-like enzyme, role in glycogen degradation unclear.221
 amyA43.2Cytoplasmic α-amylase, not MalT dependent, no apparent role in glycogen degradation.198
 galU27.8UDP-glucose pyrophosphorylase. Possible origin of cytoplasmic unphosphorylated glucose.292
 glgS68.7Short polypeptide, involved in RpoS-dependent glycogen synthesis.11, 118
 glk54.0Glucokinase. Reduces level of internal glucose which can form endogenous inducer, responsible formal gene repression at high osmolarity.43, 95, 161
 treR96.2Repressor fortreB and treC. treR mutants allow transport of maltose via the treB-encoded transport system and inducetreC, whose product is involved in inducer synthesis.129
 treB96.1Enzyme II for trehalose of the PTS, allows transport of maltose.142
 treC96.1Trehalose-6-phosphate hydrolase, involved in inducer synthesis.21
 pgm15.4Phosphoglucomutase. Needed for the synthesis of endogenous inducer. A pgm mutant can still grow on maltose but only in the presence of MalZ.1, 69, 153, 220
Genes that affect mal gene expression by an unknown mechanism when mutated
 asuE25.6tRNA-modifying enzyme. An asuE mutant increases mal gene expression at high osmolarity.262
 yjeA(genX)94.4Homolog to lysyl-tRNA synthases LysS and LysU. A genX mutant interferes with the ability of amalQ malZ292 pgm strain to grow on maltose.146, 170
 envZ76.1Sensor kinase of the two-component osmoregulatory system. Certain envZ mutants that lead to the overphosphorylation of OmpR show reducedmalT expression.33
 phoP phoQ25.7Two-component system responding to Mg2+starvation. Overexpression of the response regulator leads tomal gene repression.278, 283