The K-C channel in the cbb(3)-type respiratory oxygen reductase from rhodobacter capsulatus Is required for both chemical and pumped protons

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Küçük Resim

Tarih

2014

Dergi Başlığı

Dergi ISSN

Cilt Başlığı

Yayıncı

Amer Soc Microbiology

Erişim Hakkı

info:eu-repo/semantics/openAccess

Özet

The heme-copper superfamily of proton-pumping respiratory oxygen reductases are classified into three families (A, B, and C families) based on structural and phylogenetic analyses. Most studies have focused on the A family, which includes the eukaryotic mitochondrial cytochrome c oxidase as well as many bacterial homologues. Members of the C family, also called the cbb(3)-type oxygen reductases, are found only in prokaryotes and are of particular interest because of their presence in a number of human pathogens. All of the heme-copper oxygen reductases require proton-conducting channels to convey chemical protons to the active site for water formation and to convey pumped protons across the membrane. Previous work indicated that there is only one proton-conducting input channel (the K-C channel) present in the cbb(3)-type oxygen reductases, which, if correct, must be utilized by both chemical protons and pumped protons. In this work, the effects of mutations in the KC channel of the cbb(3)-type oxygen reductase from Rhodobacter capsulatus were investigated by expressing the mutants in a strain lacking other respiratory oxygen reductases. Proton pumping was evaluated by using intact cells, and catalytic oxygen reductase activity was measured in isolated membranes. Two mutations, N346M and Y374F, severely reduced catalytic activity, presumably by blocking the chemical protons required at the active site. One mutation, T272A, resulted in a substantially lower proton-pumping stoichiometry but did not inhibit oxygen reductase activity. These are the first experimental data in support of the postulate that pumped protons are taken up from the bacterial cytoplasm through the K-C channel.

Açıklama

Anahtar Kelimeler

Kaynak

Journal Of Bacteriology

WoS Q Değeri

Q2

Scopus Q Değeri

Q1

Cilt

196

Sayı

10

Künye