The interaction between aspartic acid 237 and lysine 358 in the lactose carrier of Escherichia coli

Steven C. King, Christian L. Hansen, T. Hastings Wilson

Research output: Contribution to journalArticle

122 Scopus citations

Abstract

The lacY from Escherichia coli strains 020 and AE43 have been cloned on plasmids which were designated p020-K358T and pAE43-D237N. These lacY mutants contain amino acid substitutions changing Lys-358 to Thr or Asp-237 to Asn, respectively. The charge neutralizing effect of each mutation is associated with a functional defect in melibiose transport which we exploited in order to isolate second site revertants to th melibiose-positive phenotype. Eleven melibiose-positive revertants of p020-K358T were isolated. All contained a second-site mutation converting Asp-237 to a neutral amino acid (8 to Asn, 1 to Gly, and 2 to Tyr). Twelve melibiose-positive revertants of pAE43-D237N were isolated. Two were second-site revertants converting Lys-358 to a neutrally Gln residue, while the remainder directly reverted Asn-237 to the wild-type Asp-237. We conclude that the functional intimate relationship between Asp-237 and Lys-358 suggests that these residues may be closely juxtaposed in three-dimensional space, possibly forming a 'charge-neutralizing' salt bridge.

Original languageEnglish (US)
Pages (from-to)177-186
Number of pages10
JournalBBA - Biomembranes
Volume1062
Issue number2
DOIs
StatePublished - Feb 25 1991

Keywords

  • Aspartic acid 237
  • Cotransport
  • Lactose carrier
  • Lysine 358
  • Membrane transport

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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