Lac permease of Escherichia coli: arginine-302 as a component of the postulated proton relay

Dr, Menick; Carrasco, Nancy; Antes, Lisa M.; Patel, Lekha; Hr, Kaback

doi:10.1021/bi00395a012

Cited by 88 publications

(57 citation statements)

References 17 publications

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“…A great deal of work has been directed towards the role of His-322 in LacY [11,12]. This residue has been implicated in lactose-coupled H ÷ translocation and forms part of a putative proton relay [245][246][247][248][249]. The proton or charge relay mechanism assumes a role for His-322, Glu-325 (which should be on the same side of a-helix X as His-322), and Arg-302 (putative helix IX) in proton translocation, which is based on analogies with proton transfer via Asp, His and Ser in serine-type proteinases [250].…”

Section: Vii-a Histidine Residuesmentioning

confidence: 99%

“…His-322 is poised to accept a proton from Glu-325 and subsequent transfer of this proton to Arg-302, another residue or the medium would lead to net proton translocation. A role for Arg-302 in proton translocation comes from the analysis of LacY(Arg-302) mutants which display properties similar to those of LacY(His-322) mutants [11,248]. More recently, the role of His-322 in proton translocation has been questioned, since the requirement for an ionizable histidine residue at position 322 in LacY is not always applicable to galactoside accumulation and galactoside-dependent proton transport [251][252][253][254].…”

Section: Vii-a Histidine Residuesmentioning

confidence: 99%

“…Several of the mutants have alterations at or nearby residues that have been implicated in the energy transduction mechanism (Fig. 8A), i.e., His-322 (one of the 'proton relay' residues) [252,253,293], Lys-319 which is on the same face of putative helix X as His-322 and Glu-325 [294], Ile-303 and Ser-306 which are close to Arg-302 (one of the 'proton releay' residues) [248,255]. Finally, mutations at more than 200 positions in Lacy have been isolated at this moment (Kaback, H.R., personal communication) of which only a few are essential for galactoside-H + symport (Glu-325, and perhaps Glu-269), and a limited number of residues affect the sugar recognition and/or the translocation process in a more or less specific manner (Fig.…”

Section: Vii-e Cation and Substrate Specificity Mutantsmentioning

confidence: 99%

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Secondary solute transport in bacteria

Poolman

Konings

1993

Biochimica et Biophysica Acta (BBA) - Bioenergetics

202

160

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Section: Vii-a Histidine Residuesmentioning

confidence: 99%

Section: Vii-a Histidine Residuesmentioning

confidence: 99%

Section: Vii-e Cation and Substrate Specificity Mutantsmentioning

confidence: 99%

See 1 more Smart Citation

Secondary solute transport in bacteria

Poolman

Konings

1993

Biochimica et Biophysica Acta (BBA) - Bioenergetics

202

160

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“…Two important residues of the lactose permease, His-322 and Glu-325 (2,3,11,24), are both conserved. The third residue, Arg-302, which is also involved in the putative charge relay system (13), is not conserved.…”

Section: Figmentioning

confidence: 99%

Lactose metabolism in Lactobacillus bulgaricus: analysis of the primary structure and expression of the genes involved

1991

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The genes coding for the lactose permease and 0-galactosidase, two proteins involved in the metabolism of lactose by LactobaciUlus bulgaricus, have been cloned, expressed, and found functional in Escherichia coli. The nucleotide sequences of these genes and their flanking regions have been determined, showing the presence of two contiguous open reading frames (ORFs). One of these ORFs codes for the lactose permease gene, and the other codes for the P-galactosidase gene. The lactose permease gene is located in front of the I-galactosidase gene, with 3 bp in the intergenic region. The two genes are probably transcribed as one operon. Primer extension studies have mapped a promoter upstream from the lactose permease gene but not the ,-galactosidase gene. This promoter is similar to those found in E. coli with general characteristics of GC-rich organisms. In addition, the sequences around the promoter contain a significantly higher number of AT base pairs (80%) than does the overall L. bulgaricus genome, which is rich in GC (GC content of 54%). The amino acid sequences obtained from translation of the ORFs are found to be highly homologous (similarity of 75%) to those from Streptococcus thermophilus. The first 460 amino acids of the lactose permease shows homology to the melibiose transport protein of E. coli. Little homology was found between the lactose permease of L. bulgaricus and E. coli, but the residues which are involved in the binding and the transport of lactose are conserved. The carboxy terminus is similar to that of the enzyme Ill of several phosphoenolpyruvate-dependent phosphotransferase systems.Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus) and Streptococcus thermophilus are dairy lactic acid bacteria that are widely used in the fermentation of milk (25). During their growth in milk, lactose is used as the primary energy source. Two systems for transport and metabolism of lactose are known in lactic acid bacteria: (i) a phosphoenolpyruvate (PEP) lactose phosphotransferase system (PTS) with a phospho-p-galactosidase enzyme (21) and (ii) a lactose permease system with a P-galactosidase. The PEP-PTS system is found in many species, including lactococci (reviewed in references 30 and 31).L. bulgaricus utilizes lactose via the second pathway. Lactose is brought into the cell as the free sugar and cleaved by P-galactosidase. The glucose moiety of the sugar is further metabolized while the galactose moiety is released (8, 23). The lactose operon of Escherichia coli, which also has a lactose permease (lacY) and 3-galactosidase (lacZ), has been extensively studied, and the proteins involved are being characterized (1-4, 11, 13, 24). Not much is known, however, about the system in lactic acid bacteria. Recently, there has been a report on the cloning and sequencing of the ,-galactosidase gene from L. bulgaricus (28). This group found that ,B-galactosidase from L. bulgaricus has an average similarity of 34% to that from E. coli, with stretches of high homology around the regions involved in activit...

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“…The effects of site-directed mutagenesis on the functional properties of the permease suggest that Arg302 in putative helix IX and His322 and Glu325 in helix X (Menick et al, 1987b;Piittner et al, 1986;Carrasco et al, 1986) the sugar recognition properties of the lac permease are altered by substitutions nearby [Ser306, Lys3 19 (Collins & Brooker, 1989), and Pro327 (Lolkema and Kaback, unpublished results)] or within the putativecharge relay [His-322 (Franc0 et al, 1989)]. …”

mentioning

confidence: 99%