Substrate selectivity of squalene synthetase

The five members of the mammalian G subfamily of ATP-binding cassette transporters differ greatly in their substrate specificity. Four members of the subfamily are important in lipid transport and the wide substrate specificity of one of the members, ABCG2, is of significance due to its role in multidrug resistance. To explore the origin of substrate selectivity in members 1, 2, 4, 5 and 8 of this subfamily, we have analysed the differences in conservation between members in a multiple sequence alignment of ABCG sequences from mammals. Mapping sets of residues with similar patterns of conservation onto the resolved 3D structure of ABCG2 reveals possible explanations for differences in function, via a connected network of residues from the cytoplasmic to transmembrane domains. In ABCG2, this network of residues may confer extra conformational flexibility, enabling it to transport a wider array of substrates.

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Bottlebrush Block Copolymer Assembly in Ultraconfined Films: Effect of Substrate Selectivity

Macromolecules ◽

10.1021/acs.macromol.0c02057 ◽

2021 ◽

Vol 54 (5) ◽

pp. 2079-2089

Author(s):

Yaron Aviv ◽

Esra Altay ◽

Ofer Burg ◽

Marcus Müller ◽

Javid Rzayev ◽

...

Keyword(s):

Block Copolymer ◽

Substrate Selectivity ◽

Block Copolymer Assembly ◽

Copolymer Assembly

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Contribution of Linear Free Energy Relationships to Isozyme- and pH-Dependent Substrate Selectivity of Glutathione S-Transferases: Comparison of Model Studies and Enzymatic Reactions

Journal of the American Chemical Society ◽

10.1021/ja980816o ◽

1998 ◽

Vol 120 (27) ◽

pp. 6651-6660 ◽

Cited By ~ 5

Author(s):

Brenda S. Nieslanik ◽

William M. Atkins

Keyword(s):

Free Energy ◽

Enzymatic Reactions ◽

Substrate Selectivity ◽

Linear Free Energy Relationships ◽

Model Studies ◽

Linear Free Energy ◽

Glutathione S Transferases ◽

Energy Relationships ◽

Ph Dependent

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Kinetics and Metabolism of Bifidobacterium adolescentis MB 239 Growing on Glucose, Galactose, Lactose, and Galactooligosaccharides

Applied and Environmental Microbiology ◽

10.1128/aem.02914-06 ◽

2007 ◽

Vol 73 (11) ◽

pp. 3637-3644 ◽

Cited By ~ 62

Author(s):

Alberto Amaretti ◽

Tatiana Bernardi ◽

Elena Tamburini ◽

Simona Zanoni ◽

Mariella Lomma ◽

...

Keyword(s):

Growth Rate ◽

Recursive Algorithm ◽

Carbon Fluxes ◽

Degree Of Polymerization ◽

Substrate Selectivity ◽

Carbon Distribution ◽

Bifidobacterium Adolescentis ◽

Fermentation Products ◽

Batch Cultures ◽

Ethanol Yields

ABSTRACT The kinetics and the metabolism of Bifidobacterium adolescentis MB 239 growing on galactooligosaccharides (GOS), lactose, galactose, and glucose were investigated. An unstructured unsegregated model for growth in batch cultures was developed, and kinetic parameters were calculated with a recursive algorithm. The growth rate and cellular yield were highest on galactose, followed by lactose and GOS, and were lowest on glucose. Lactate, acetate, and ethanol yields allowed the calculation of carbon fluxes toward fermentation products. Distributions between two- and three-carbon products were similar on all the carbohydrates (55 and 45%, respectively), but ethanol yields were different on glucose, GOS, lactose, and galactose, in decreasing order of production. Based on the stoichiometry of the fructose-6-phosphate shunt and on the carbon distribution among the products, the ATP yield was calculated. The highest yield was obtained on galactose, while the yields were 5, 8, and 25% lower on lactose, GOS, and glucose, respectively. Therefore, a correspondence among ethanol production, low ATP yields, and low biomass production was established, demonstrating that carbohydrate preferences may result from different distributions of carbon fluxes through the fermentative pathway. During the fermentation of a GOS mixture, substrate selectivity based on the degree of polymerization was exhibited, since lactose and the trisaccharide were the first to be consumed, while a delay was observed until longer oligosaccharides were utilized. Throughout the growth on both lactose and GOS, galactose accumulated in the cultural broth, suggesting that β(1-4) galactosides can be hydrolyzed before they are taken up.

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