A binding protein-dependent transport system in Streptococcus mutans responsible for multiple sugar metabolism.
05 Mar 1992-Journal of Biological Chemistry (American Society for Biochemistry and Molecular Biology)-Vol. 267, Iss: 7, pp 4631-4637
TL;DR: An 11-kilobase gene region of Streptococcus mutans has been identified which contains eight contiguous genes involved with the uptake and metabolism of multiple sugars (the msm system), and Insertional inactivation of each of these genes along with uptake data indicate that this system is responsible for the uptake of melibiose, raffinose, and isomaltotriose.
About: This article is published in Journal of Biological Chemistry.The article was published on 1992-03-05 and is currently open access. It has received 254 citations till now. The article focuses on the topics: Structural gene & Operon.
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TL;DR: The availability of an increasing number of high-resolution structures has provided a valuable framework for interpretation of recent studies, and realistic models have been proposed to explain how these fascinating molecular machines use complex dynamic processes to fulfill their numerous biological functions.
Abstract: Summary: ATP-binding cassette (ABC) systems are universally distributed among living organisms and function in many different aspects of bacterial physiology. ABC transporters are best known for their role in the import of essential nutrients and the export of toxic molecules, but they can also mediate the transport of many other physiological substrates. In a classical transport reaction, two highly conserved ATP-binding domains or subunits couple the binding/hydrolysis of ATP to the translocation of particular substrates across the membrane, through interactions with membrane-spanning domains of the transporter. Variations on this basic theme involve soluble ABC ATP-binding proteins that couple ATP hydrolysis to nontransport processes, such as DNA repair and gene expression regulation. Insights into the structure, function, and mechanism of action of bacterial ABC proteins are reported, based on phylogenetic comparisons as well as classic biochemical and genetic approaches. The availability of an increasing number of high-resolution structures has provided a valuable framework for interpretation of recent studies, and realistic models have been proposed to explain how these fascinating molecular machines use complex dynamic processes to fulfill their numerous biological functions. These advances are also important for elucidating the mechanism of action of eukaryotic ABC proteins, because functional defects in many of them are responsible for severe human inherited diseases.
1,194 citations
Cites background from "A binding protein-dependent transpo..."
...First, a single BP can have a wide substrate specificity, as illustrated by the multiple-sugar transporter Msm of Streptococcus mutans, which recognizes melibiose, sucrose, raffinose, isomaltotriose, and isomaltotetraose (409, 474)....
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TL;DR: The genome analysis provides further insight into how S. mutans has adapted to surviving the oral environment through resource acquisition, defense against host factors, and use of gene products that maintain its niche against microbial competitors.
Abstract: Streptococcus mutans is the leading cause of dental caries (tooth decay) worldwide and is considered to be the most cariogenic of all of the oral streptococci. The genome of S. mutans UA159, a serotype c strain, has been completely sequenced and is composed of 2,030,936 base pairs. It contains 1,963 ORFs, 63% of which have been assigned putative functions. The genome analysis provides further insight into how S. mutans has adapted to surviving the oral environment through resource acquisition, defense against host factors, and use of gene products that maintain its niche against microbial competitors. S. mutans metabolizes a wide variety of carbohydrates via nonoxidative pathways, and all of these pathways have been identified, along with the associated transport systems whose genes account for almost 15% of the genome. Virulence genes associated with extracellular adherent glucan production, adhesins, acid tolerance, proteases, and putative hemolysins have been identified. Strain UA159 is naturally competent and contains all of the genes essential for competence and quorum sensing. Mobile genetic elements in the form of IS elements and transposons are prominent in the genome and include a previously uncharacterized conjugative transposon and a composite transposon containing genes for the synthesis of antibiotics of the gramicidin/bacitracin family; however, no bacteriophage genomes are present.
984 citations
TL;DR: The phylogenetic relationship suggests that members of the AraC/XylS family have recruited the nonconserved domain(s) into a series of existing domains involved in DNA recognition and transcription stimulation and that this recruited domain governs the role that the regulator carries out.
Abstract: The ArC/XylS family of prokaryotic positive transcriptional regulators includes more than 100 proteins and polypeptides derived from open reading frames translated from DNA sequences. Members of this family are widely distributed and have been found in the gamma subgroup of the proteobacteria, low- and high-G + C-content gram-positive bacteria, and cyanobacteria. These proteins are defined by a profile that can be accessed from PROSITE PS01124. Members of the family are about 300 amino acids long and have three main regulatory functions in common: carbon metabolism, stress response, and pathogenesis. Multiple alignments of the proteins of the family define a conserved stretch of 99 amino acids usually located at the C-terminal region of the regulator and connected to a nonconserved region via a linker. The conserved stretch contains all the elements required to bind DNA target sequences and to activate transcription from cognate promoters. Secondary analysis of the conserved region suggests that it contains two potential alpha-helix-turn-alpha-helix DNA binding motifs. The first, and better-fitting motif is supported by biochemical data, whereas existing biochemical data neither support nor refute the proposal that the second region possesses this structure. The phylogenetic relationship suggests that members of the family have recruited the nonconserved domain(s) into a series of existing domains involved in DNA recognition and transcription stimulation and that this recruited domain governs the role that the regulator carries out. For some regulators, it has been demonstrated that the nonconserved region contains the dimerization domain. For the regulators involved in carbon metabolism, the effector binding determinants are also in this region. Most regulators belonging to the AraC/XylS family recognize multiple binding sites in the regulated promoters. One of the motifs usually overlaps or is adjacent to the -35 region of the cognate promoters. Footprinting assays have suggested that these regulators protect a stretch of up to 20 bp in the target promoters, and multiple alignments of binding sites for a number of regulators have shown that the proteins recognize short motifs within the protected region.
730 citations
TL;DR: The occurrence of two distinct classes of bacterial cytoplasmic repressor proteins which are homologous to two different clusters of periplasmic binding proteins suggests that the gene-splicing events which allowed functional conversion of these proteins with retention of domain structure have occurred repeatedly during evolutionary history.
701 citations
TL;DR: The characteristics of adhesin and receptor molecules and the potential roles they play in dental plaque accretion are reviewed.
Abstract: The oral cavity is home to a large and diverse population of microbes comprising over 350 taxa and in which 37 genera of bacteria are represented (37, 38). Coaggregation, or cellto-cell recognition of genetically distinct partner cell-types, has been observed with isolates from the 18 genera tested so far (25, 26); these 18 genera constitute the bacteria most frequently isolated from dental plaque. Like other saprophytic and pathogenic bacteria that inhabit or invade various human tissues, members of the oral flora possess specific cell surface-associated adherence proteins responsible for initiating colonization. These bacterial adhesins recognize protein, glycoprotein, or polysaccharide receptors on various oral surfaces, including other cell types. In dental plaque, the ability to attach to bacteria already anchored to hard or soft tissues may provide secondary colonizers with the same advantages enjoyed by primary colonizers. Essentially all oral bacteria possess surface molecules that foster some sort of cell-to-cell interaction (26); some constitutively synthesize a coterie of adhesins that permit a cell to participate simultaneously in multiple interactions with partner cell types (32). Other oral bacteria, such as the cariogenic mutans streptococci, synthesize extracellular glucans and a major surface protein antigen (14) that contribute to their ability to adhere to teeth (29). This kind of adherence has been extensively studied by many laboratories and appears to be distinct from coaggregation. In other ecosystems, there is surprisingly little or no evidence for coaggregation among resident bacteria. Juxtapositioning of genetically unrelated bacterial microcolonies in metabolic consortia performing anaerobic biodegradations (36, 49) is different from coaggregations which are characterized by direct and viability-independent cell-to-cell recognition. Bacterial predation and conjugation, the action of the pheromone system of Enterococcus faecalis (44), invertebrate animal intestinal tract microbes (5), and nutritional symbionts have some similarities to the highly specific mechanisms of oral bacterial recognition. Coaggregation may be intra-, interor multigeneric, and it is different from the interactions among clonal populations, for example rosettes among caulobacters. Generally, secondary colonizers synthesize protein adhesins that recognize receptors on primary colonizers such as the streptococci and actinomyces (30). This review will deal with the characteristics of adhesin and receptor molecules and the potential roles they play in dental plaque accretion. Equally important to adherence in developing oral microbial consortia are the nutritional relationships among plaque bacteria, which have been reviewed elsewhere (26) and will not be discussed further here.
669 citations
Cites background from "A binding protein-dependent transpo..."
...There is a growing awareness that these gram-positive lipoproteins (18, 25, 40) may be involved in more general recognition functions, such as the binding protein-dependent transport systems reported for numerous gram-negative bacteria....
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References
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