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A prolonged digestion of colicin E1 with dilute trypsin results in the generation of a trypsin-resistant peptide fragment of the colicin which is approximately one-third of the molecule. The amino acid composition of the fragment, Mr = 20,000, is more nonpolar in nature than the colicin, with the major change in composition being the reduction of the(More)
Salmonella typhimurium synthesizes cobalamin (vitamin B12) when grown under anaerobic conditions. All but one of the biosynthetic genes (cob) are located in a single operon which includes genes required for the production of cobinamide and dimethylbenzimidazole, as well as the genes needed to form cobalamin from these precursors. We isolated strains(More)
The pyruvate oxidase structural gene (poxB) of Escherichia coli was cloned into derivatives of plasmid pBR322. The gene was first cloned into a cosmid vector by selection for the tetracycline resistance determinant of a closely linked Tn10 insertion (no direct selection for the gene was available). Subsequent subcloning resulted in localization of the gene(More)
The entire nucleotide sequence of the poxB (pyruvate oxidase) gene of Escherichia coli K-12 has been determined by the dideoxynucleotide (Sanger) sequencing of fragments of the gene cloned into a phage M13 vector. The gene is 1716 nucleotides in length and has an open reading frame which encodes a protein of Mr 62,018. This open reading frame was shown to(More)
The pyruvate oxidase of Escherichia coli is a peripheral membrane flavoprotein that is dramatically activated by lipids. The enzyme strongly binds to phospholipid vesicles in vitro. In vivo, in addition to enzyme activation, binding is thought to be important to provide access of the enzyme to ubiquinone dissolved in the lipid bilayer. It was unclear if(More)
Escherichia coli pyruvate oxidase is a membrane-associated flavoprotein dehydrogenase which is greatly activated by lipids and detergents. The carboxyl-terminal region of the protein has been shown to play a critical role in the interaction with lipids. We report mutations generated by chemical and oligonucleotide-mediated site-directed mutagenesis of the(More)
The pyruvate oxidase of Escherichia coli is a homo-tetrameric enzyme which can be activated greater than 500-fold (kcat/Km) by limited proteolytic digestion with alpha-chymotrypsin in the presence of pyruvate and thiamine pyrophosphate. The cleavage produces an Mr 2000 peptide (the alpha-peptide) from each subunit and mimics the physiologically important(More)
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