Gene fusions with β-lactamase show that subunit I of the cytochrome bd quinol oxidase from E. coli has nine transmembrane helices with the O 2 reactive site near the periplasmic surface

Jie Zhang, Blanca Barquera, Robert B. Gennis

Research output: Contribution to journalArticle

33 Scopus citations


The cytochrome bd quinol oxidase is a component of the respiratory chain of many prokaryotes. The enzyme contains two subunits, CydA and CydB, which were initially predicted based on the sequence of the Escherichia coli oxidase to have seven and eight transmembrane spans, respectively. More recently, the topological model of CydA was revised to predict nine transmembrane helices, based on additional sequence information from other organisms. In the current work, the topology of the E. coli oxidase was experimentally examined using β-lactamase gene fusions. The results confirm the revised topology, which places the oxygen reactive site near the periplasmic surface.

Original languageEnglish (US)
Pages (from-to)58-62
Number of pages5
JournalFEBS Letters
Issue number1-3
StatePublished - Mar 12 2004


Cite this