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I C Sutcliffe

Publications and source records attributed to I C Sutcliffe.

25 records · Page 2Linked to original sources
PubMed1993

Cloning and expression of the multiple sugar metabolism (msm) operon of Streptococcus mutans in heterologous streptococcal hosts.

The multiple sugar metabolism (msm) operon of Streptococcus mutans is responsible for the uptake and metabolism of a variety of sugars. In order to further characterize the substrate specificities of the transport system, a 12-kb region of DNA containing the entire msm operon was cloned, via a novel two-step integration strategy, into the chromosomes of two heterologous streptococcal strains, Streptococcus gordonii Challis and Streptococcus anginosus Is57, as well as the chromosome of a natural isolate of S. mutans with a deletion of the msm region. These strains are unable to transport or ferment melibiose, raffinose, or isomaltosaccharides, but the newly constructed recombinants gained the ability to ferment all of these sugars. The S. gordonii Challis construct containing msm was shown to transport radiolabelled melibiose, raffinose, isomaltotriose, and isomaltotetraose, and the transport function was also subjected to induction by raffinose, an inducer of the msm operon in S. mutans. The results confirm the role of the msm operon in the transport and metabolism of melibiose, raffinose, and isomaltosaccharides.

Biological Transport↗
PubMed1993

MsmE, a lipoprotein involved in sugar transport in Streptococcus mutans.

Metabolic labelling by [14C]palmitic acid showed that growth of Streptococcus mutans LT11 in raffinose, an inducer of the msm operon, resulted in increased production of a 45-kDa lipoprotein corresponding to MsmE, which is believed to be a sugar-binding protein. MsmE was also labelled when an msmE clone was expressed in Escherichia coli. The presence of a lipid anchor on MsmE provides a likely explanation of how the sugar-binding protein component of the msm binding protein-dependent multiple sugar transport system is retained at the cell surface.

Amino Acid Sequence↗
PubMed1993

Transport of sugars, including sucrose, by the msm transport system of Streptococcus mutans.

The range of substrates transported by the sugar-binding protein-dependent msm (multiple sugar metabolism) system of S. mutans was investigated. By determining the ability of unlabeled sugar to compete with radiolabeled melibiose transport, we have demonstrated that the transported sugars included a number of carbohydrates structurally related to raffinose. A model accommodating these results has been devised which accounts for the sugars transported by the msm transport system. Competition with radiolabeled melibiose transport indicated sucrose to be an msm substrate. This was confirmed by examination of uptake of radiolabeled sucrose in scrAB mutants lacking the sucrose-specific phosphotransferase system.

Biological Transport↗
PubMed1993

Abnormal activation of glycogen synthesis in fibroblasts from NIDDM subjects. Evidence for an abnormality specific to glucose metabolism.

To determine whether the tendency for NIDDM to run in families could relate to genetically determined defects in insulin stimulation of glycogen synthesis, skin fibroblasts from subjects with a strong family history of NIDDM were studied. Fibroblasts from nondiabetic subjects without any family history of NIDDM were studied as control subjects. The cells were studied after 7-16 passages in culture. Rates of glycogen synthesis were lower in fibroblasts from NIDDM subjects both basally and with maximal insulin stimulation (0.77 +/- 0.11 vs. 0.46 +/- 0.04 pmol.well-1 x h-1 [P < 0.02] and 1.49 +/- 0.26 vs. 0.69 +/- 0.05 pmol.well-1 x h-1 +adP < 0.01]). Rates of glycogen synthesis were stimulated 1.9 +/- 0.2-fold above basal in the control cells and 1.5 +/- 0.1-fold above basal in the NIDDM cells (P < 0.02). Rates of [3H]thymidine uptake were similar in control and NIDDM fibroblasts (basal, 28.3 +/- 2.8 vs. 39.2 +/- 8.0; maximum, 50.9 +/- 7.2 vs. 69.3 +/- 16.9 dpm x 10(-3), respectively). Rates of uptake increased similarly in control and NIDDM cells by 1.8 +/- 0.1- and 1.7 +/- 0.1-fold above basal. Maximum specific fibroblast insulin binding was similar for control and NIDDM subjects (194.0 +/- 29.2 vs. 176.1 +/- 24.9 fmol 125I-labeled insulin bound/mg protein respectively). The tyrosine kinase activity of insulin receptors isolated from the control and NIDDM fibroblasts was similar (basal, 135 +/- 30 vs. 149 +/- 33; submaximal, 153 +/- 28 vs. 155 +/- 30; and maximal insulin, 191 +/- 45 vs. 213 +/- 48 dpm.mg protein-1 x min-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1992

A binding protein-dependent transport system in Streptococcus mutans responsible for multiple sugar metabolism.

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). Sequence analysis of this region indicates that several of these genes specify proteins with strong homology to components of periplasmic binding protein-dependent transport systems of Gram-negative bacteria. Additionally, this operon is controlled by a regulatory gene (msmR) that acts as a positive effector. The proteins specified by the structural genes of the msm operon include alpha-galactosidase (aga), a "periplasmic-like" sugar-binding protein (msmE), two membrane proteins (msmF, msmG), sucrose phosphorylase (gtfA), an ATP-binding protein (msmK), and dextran glucosidase (dexB). 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 and the metabolism of melibiose, sucrose, and isomaltosaccharides.

Amino Acid Sequence↗
PubMedDate not supplied

Cell envelope composition and organisation in the genus Rhodococcus.

A knowledge of the organisation of the rhodococcal cell envelope is of fundamental importance if the environmental and biotechnological significance of these bacteria are to be understood and successfully exploited. The genus Rhodococcus belongs to a distinctive suprageneric taxon, the mycolata, which includes among others the genera Corynebacterium, Mycobacterium and Nocardia. Members of this taxon exhibit an unusual complexity in their cell envelope composition and organisation compared to other Gram-positive bacteria. Models that describe the architecture of the mycobacterial cell envelope are extrapolated here to provide a model of the rhodococcal cell envelope. The rhodococcal cell envelope is dominated by the presence of an arabinogalactan cell wall polysaccharide and large 2-alkyl 3-hydroxy branched-chain fatty acids, the mycolic acids, which are covalently assembled into a peptidoglycan-arabinogalactan-mycolic acid matrix. This review further emphasises that the mycolic acids in this complex form the basis of an outer lipid permeability barrier. The localisation and roles of other cell envelope components, notably complex free lipids, lipoglycans, proteins and lipoproteins are also considered.

Cell Membrane↗