A 19F-NMR study of the membrane-binding region of D-lactate dehydrogenase of Escherichia coli.
Related Articles A 19F-NMR study of the membrane-binding region of D-lactate dehydrogenase of Escherichia coli.
Protein Sci. 1993 Nov;2(11):1938-47
Authors: Sun ZY, Truong HT, Pratt EA, Sutherland DC, Kulig CE, Homer RJ, Groetsch SM, Hsue PY, Ho C
D-Lactate dehydrogenase (D-LDH) is a membrane-associated respiratory enzyme of Escherichia coli. The protein is composed of 571 amino acid residues with a flavin adenine dinucleotide (FAD) cofactor, has a molecular weight of approximately 65,000, and requires lipids or detergents for full activity. We used NMR spectroscopy to investigate the structure of D-LDH and its interaction with phospholipids. We incorporated 5-fluorotryptophan (5F-Trp) into the native enzyme, which contains five tryptophan residues, and into mutant enzymes, where a sixth tryptophan is substituted into a specific site by oligonucleotide-directed mutagenesis, and studied the 5F-Trp-labeled enzymes using 19F-NMR spectroscopy. In this way, information was obtained about the local environment at each native and substituted tryptophan site. Using a nitroxide spin-labeled fatty acid, which broadens the resonance from any residue within 15 A, we have established that the membrane-binding area of the protein includes the region between Tyr 228 and Phe 369, but is not continuous within this region. This conclusion is strengthened by the results of 19F-NMR spectroscopy of wild-type enzyme labeled with fluorotyrosine or fluorophenylalanine in the presence and absence of a nitroxide spin-labeled fatty acid. These experiments indicate that 9-10 Phe and 3-4 Tyr residues are located near the lipid phase.
PMID: 8268803 [PubMed - indexed for MEDLINE]
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PubMed