1efp
From Proteopedia
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ELECTRON TRANSFER FLAVOPROTEIN (ETF) FROM PARACOCCUS DENITRIFICANS
Overview
The crystal structure of electron transfer flavoprotein (ETF) from, Paracoccus denitrificans was determined and refined to an R-factor of, 19.3% at 2.6 A resolution. The overall fold is identical to that of the, human enzyme, with the exception of a single loop region. Like the human, structure, the structure of the P. denitrificans ETF is comprised of three, distinct domains, two contributed by the alpha-subunit and the third from, the beta-subunit. Close analysis of the structure reveals that the loop, containing betaI63 is in part responsible for conferring the high, specificity of AMP binding by the ETF protein. Using the sequence and, structures of the human and P. denitrificans enzymes as models, a detailed, sequence alignment has been constructed for several members of the ETF, family, including sequences derived for the putative FixA and FixB, proteins. From this alignment, it is evident that in all members of the, ETF family the residues located in the immediate vicinity of the FAD, cofactor are identical, with the exception of the substitution of serine, and leucine residues in the W3A1 ETF protein for the human residues, alphaT266 and betaY16, respectively. Mapping of ionic differences between, the human and P. denitrificans ETF onto the structure identifies a surface, that is electrostatically very similar between the two proteins, thus, supporting a previous docking model between human ETF and pig medium-chain, acyl-CoA dehydrogenase (MCAD). Analysis of the ionic strength dependence, of the electron transfer reaction between either human or P. denitrificans, ETF and MCAD demonstrates that the human ETF functions optimally at low (, approximately 10 mequiv) ionic strength, while P. denitrificans ETF is a, better electron acceptor at higher (>75 mequiv) ionic strength. This, suggests that the electrostatic surface potential of the two proteins is, very different and is consistent with the difference in isoelectric points, between the proteins. Analysis of the electrostatic potentials of the, human and P. denitrificans ETFs reveals that the P. denitrificans ETF is, more negatively charged. This excess negative charge may contribute to the, difference in redox potentials between the two ETF flavoproteins and, suggests an explanation for the opposing ionic strength dependencies for, the reaction of MCAD with the two ETFs. Furthermore, by analysis of a, model of the previously described human-P. denitrificans chimeric ETF, protein, it is possible to identify one region of ETF that participates in, docking with ETF-ubiquinone oxidoreductase, the physiological electron, acceptor for ETF.
About this Structure
1EFP is a Protein complex structure of sequences from Paracoccus denitrificans with FAD and AMP as ligands. Full crystallographic information is available from OCA.
Reference
Crystal structure of Paracoccus denitrificans electron transfer flavoprotein: structural and electrostatic analysis of a conserved flavin binding domain., Roberts DL, Salazar D, Fulmer JP, Frerman FE, Kim JJ, Biochemistry. 1999 Feb 16;38(7):1977-89. PMID:10026281
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