Disease relevance of malP

• The mutation leading to the loss of protein Ib in these strains is independent of the tolF mutation and is located near malP on the E. coli genetic map [1].
• A 5,800-base pair HindIII-EcoRI DNA fragment from one of these phages was cloned into pBR322 and shown to contain malT, which is the positive regulator gene of the maltose regulon, and most of malP, the structural gene for maltodextrin phosphorylase [2].
• Genetic localization and regulation of the maltose phosphorylase gene, malP, in Lactococcus lactis [3].

High impact information on malP

• In this review, we compare crystallographic structures of regulated and unregulated phosphorylases, including maltodextrin phosphorylase (MalP) from Escherichia coli, glycogen phosphorylase from yeast, and mammalian isozymes from muscle and liver tissues [4].
• In Escherichia coli, the activity of maltodextrin phosphorylase (MalP) is controlled by induction at the level of gene expression, and the enzyme exhibits no regulatory properties [5].
• The crystal structure of E. coli maltodextrin phosphorylase co-crystallized with an oligosaccharide has been solved at 3.0 A resolution, providing the first structure of an oligosaccharide bound at the catalytic site of an alpha-glucan phosphorylase [6].
• This study demonstrates an essential role of lysine 533, the only charged residue in hydrogen bond distance to the phosphate of pyridoxal 5'-phosphate in Escherichia coli maltodextrin phosphorylase [7].
• Maltotriose and the MalT protein suffice to stimulate initiation of transcription at malPp by the E. coli RNA polymerase holoenzyme [8].

Chemical compound and disease context of malP

• To probe the interactions of acarbose with other carbohydrate recognition enzymes, the crystal structure of E. coli maltodextrin phosphorylase (MalP) complexed with acarbose has been determined at 2.95 A resolution and refined to crystallographic R-values of R (Rfree) = 0.241 (0.293), respectively [9].
• Maltodextrin phosphorylase from Escherichia coli (MalP) is a dimeric protein in which each approximately 90-kDa subunit contains active-site pyridoxal 5'-phosphate [10].
• Changes in the active site of Escherichia coli maltodextrin phosphorylase created by substituting residues Lys533, Arg534, Tyr538, and Glu637 were monitored in the absence and presence of arsenate as substrate analogue using pyridoxal-P as 31P NMR reporter [11].
• Site-directed mutagenesis of E350 to alanine in Escherichia coli maltodextrin phosphorylase reduced both enzyme activity (100-fold) and apparent binding of the oligosaccharide substrate (10-fold), suggesting a participation of this residue in binding of the substrate in the ground and transition states [12].
• Maltodextrin phosphorylase from Escherichia coli: production and application for the synthesis of alpha-glucose-1-phosphate [13].

Biological context of malP

• The other set was centered on an EcoRI site, which had been introduced close to the beginning of the malT cistron, and extended towards gene malP [14].
• The complete 796 residue amino acid sequence of maltodextrin phosphorylase was deduced from the E. coli malP nucleotide sequence [15].
• By combining all presently available information, it is suggested that the malPp promoter contains three binding sites for its activator, the product of gene malT [16].
• A plasmid bearing the malPp promoter was digested with Bal31 to obtain a set of deletions with closely spaced endpoints in the upstream region of this promoter [16].
• In the next step these fragments were transposed into the chromosome by homologous recombination events occurring on both sides of malPp [17].

Associations of malP with chemical compounds

• Uninduced malPQ transcription, as followed by measuring beta-galactosidase expression in a strain carrying a malP-lacZ hybrid gene and grown in the absence of maltose, requires the presence of CAP [18].
• The bacterial enzyme maltodextrin phosphorylase (MalP) catalyses the phosphorolysis of an alpha-1,4-glycosidic bond in maltodextrins, removing the non-reducing glucosyl residues of linear oligosaccharides as glucose-1-phosphate (Glc1P) [19].
• The MalT sites in malPp were precisely located and their occupation as a function of MalT concentration was quantified using DNase I and dimethyl sulphate footprinting experiments [20].
• Likewise, in an in vitro transcription system, initiation of transcription at malPp required the presence of the MalT protein and maltotriose along with the RNA polymerase holoenzyme; neither maltose nor maltotetraose could substitute for maltotriose [21].

Regulatory relationships of malP

• Using in vitro techniques we have fused upstream sequences from the malPp promoter (normally activated by the MalT protein) to downstream sequences from the lacZp promoter (normally repressed by the LacI protein) [22].

Other interactions of malP

• The sequences of the coding regions and of elements known to be important for the functions of these two promoters in E. coli were well conserved between the two bacteria, whereas the sequence of the malT-malP intergenic region had totally diverged [23].
• The cloned region which follows glgA contains an incomplete ORF (1149 bp), glgY, which appears to encode 383 aa of the N terminus of glycogen phosphorylase, based upon sequence similarity with the enzyme from rabbit muscle (47% identical aa residues) and with maltodextrin phosphorylase from E. coli (37% identical aa residues) [24].

Analytical, diagnostic and therapeutic context of malP

• Substrate analogs are used in combination with site-directed mutagenesis to probe specific interactions between substrate and enzyme in the forward and reverse direction of the Escherichia coli maltodextrin phosphorylase reaction [25].
• Crystallization and crystallographic data of Escherichia coli maltodextrin phosphorylase [26].
• Efficient downstream processing of maltodextrin phosphorylase from Escherichia coli and stabilization of the enzyme by immobilization onto hydroxyapatite [27].

References