Analysis of the structural specificity of the lactose permease toward sugars

S. G. Olsen, Robert J Brooker

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The sugar specificity properties of the lactose permease were investigated. Free galactose was shown to competitively inhibit the lactose permease yielding a K(i) value of 7.4 mM. This value was severalfold higher than the observed K(m) for lactose (1.3 mM). A variety of other monosaccharides also showed significant inhibition of lactose transport. With regard to -OH groups along the galactose ring it appears that the relative importance is OH-3 > OH-4 > OH-6 > OH-2 > OH-1. In general, galactosides with α-linkages exhibited significantly higher affinities compared with their β-linked counterparts. An optimal size for the aglycone portion of the galactoside was reached with aglycones containing hexose residues or a benzene ring. The preferred size of the aglycone appears to be hexose, benzene ring > methyl group > no aglycone ≥ disaccharide > trisaccharide. However, neither the specific structure of the aglycone nor its relative hydrophobicity appeared to be important factors in permease recognition. For example, the hydrophobic β-nitrophenyl-galactosides had lower affinities compared with lactose (a β-galactoside), whereas the α-nitrophenylgalactosides generally had higher affinities compared with melibiose (an α-galactoside). In addition, no consistent preference was seen when considering the location of the nitro group of the benzene ring. From this work, a model is presented which depicts the binding of galactoside to the lactose permease.

Original languageEnglish (US)
Pages (from-to)15982-15987
Number of pages6
JournalJournal of Biological Chemistry
Volume264
Issue number27
StatePublished - Jan 1 1989

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Galactosides
Sugars
Lactose
Benzene
Hexoses
Galactose
Nitrophenylgalactosides
Melibiose
Portion Size
Trisaccharides
Membrane Transport Proteins
Monosaccharides
Disaccharides
Hydrophobicity
Hydrophobic and Hydrophilic Interactions
lactose permease
hydroxide ion

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Analysis of the structural specificity of the lactose permease toward sugars. / Olsen, S. G.; Brooker, Robert J.

In: Journal of Biological Chemistry, Vol. 264, No. 27, 01.01.1989, p. 15982-15987.

Research output: Contribution to journalArticle

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