InterPro : IPR023461

Name  Electron transfer flavoprotein, FixB subunit Short Name  ETF_FixBsu
Type  Family Description  Electron transfer flavoproteins (ETFs) serve as specific electron acceptors for primary dehydrogenases, transferring the electrons to terminal respiratory systems. They can be functionally classified into constitutive, "housekeeping" ETFs, mainly involved in the oxidation of fatty acids (Group I), and ETFs produced by some prokaryotes under specific growth conditions, receiving electrons only from the oxidation of specific substrates (Group II) []. ETFs are heterodimeric proteins composed of an alpha and beta subunit, and contain an FAD cofactor and AMP [, , , , ]. ETF consists of three domains: domains I and II are formed by the N- and C-terminal portions of the alpha subunit, respectively, while domain III is formed by the beta subunit. Domains I and III share an almost identical alpha-beta-alpha sandwich fold, while domain II forms an alpha-beta-alpha sandwich similar to that of bacterial flavodoxins. FAD is bound in a cleft between domains II and III, while domain III binds the AMP molecule. Interactions between domains I and III stabilise the protein, forming a shallow bowl where domain II resides.The alpha subunit of both Group I and Group II ETFs is composed of domains I and II.Many enterobacteria are able to convert carnitine, via crotonobetaine, to gamma-butyrobetaine in the presence of carbon and nitrogen sources under anaerobic conditions []. In Escherichia coli the enzymes involved in this pathway are encoded by the caiTABCDE operon []. The adjacent but divergent fixABCD operon also appears to be necessary for carnintine meatbolism []. The Fix proteins are homologous to proteins found in known electron transport pathways.This entry represents the predicted electron transfer protein alpha subunit FixB, which is necessary for anaerobic carnitine reduction. FixB may be involved in transferring reductant to the CaiA protein.

Sequence Features

GO Displayer


InterPro protein domain ID --> Contigs



0 Child Features

0 Contains

0 Found In

1 Parent Features

Id Name Short Name Type
IPR001308 Electron transfer flavoprotein, alpha subunit ETF_a Family

9 Publications

First Author Title Year Journal Volume Pages
Finocchiaro G Biosynthesis, molecular cloning and sequencing of electron transfer flavoprotein. 1990 Prog Clin Biol Res 321 637-52
Tsai MH Phylogenetic characterization of the ubiquitous electron transfer flavoprotein families ETF-alpha and ETF-beta. 1995 Res Microbiol 146 397-404
Roberts DL Three-dimensional structure of human electron transfer flavoprotein to 2.1-A resolution. 1996 Proc Natl Acad Sci U S A 93 14355-60
Roberts DL Crystal structure of Paracoccus denitrificans electron transfer flavoprotein: structural and electrostatic analysis of a conserved flavin binding domain. 1999 Biochemistry 38 1977-89
Weidenhaupt M Bradyrhizobium japonicum possesses two discrete sets of electron transfer flavoprotein genes: fixA, fixB and etfS, etfL. 1996 Arch Microbiol 165 169-78
Leys D Extensive conformational sampling in a ternary electron transfer complex. 2003 Nat Struct Biol 10 219-25
Eichler K Molecular characterization of the cai operon necessary for carnitine metabolism in Escherichia coli. 1994 Mol Microbiol 13 775-86
Kleber HP Bacterial carnitine metabolism. 1997 FEMS Microbiol Lett 147 1-9
Walt A The fixA and fixB genes are necessary for anaerobic carnitine reduction in Escherichia coli. 2002 J Bacteriol 184 4044-7

To cite PlanMine, please refer to the following publication:

Rozanski, A., Moon, H., Brandl, H., Martín-Durán, J. M., Grohme, M., Hüttner, K., Bartscherer, K., Henry, I., & Rink, J. C.
PlanMine 3.0—improvements to a mineable resource of flatworm biology and biodiversity
Nucleic Acids Research, gky1070. doi:10.1093/nar/gky1070 (2018)