Galactoside-dependent proton transport by mutants of the Escherichia coli lactose carrier. Replacement of histidine 322 by tyrosine or phenylalanine

Steven King, T. Hastings Wilson

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Abstract

Mutations have been introduced into the Escherichia coli lac Y gene by oligonucleotide-directed mutagenesis such that the lactose carrier contains either tyrosine or phenylalanine in place of histidine 322. These mutants did not carry out active accumulation of lactose, melibiose, or methyl-β-D-galactopyranoside, but facilitated diffusion was still catalyzed. Galactoside-dependent H+ transport, measured with the pH electrode, was retained in both mutants. We conclude that although histidine 322 is important for energy transduction, neither an electronegative atom nor a dissociable proton is essential for proton cotransport with lactose or melibiose.

Original languageEnglish (US)
Pages (from-to)7390-7394
Number of pages5
JournalJournal of Biological Chemistry
Volume264
Issue number13
Publication statusPublished - 1989
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry

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