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Title

The Long and Short Flavodoxins. I. i. the role of the differentiating loop in apoflavodoxin structure and fmn

AuthorsLópez-Llano, Jon; Maldonado, Susana; Bueno, Marta; Lostao, Anabel; Jiménez, M. Angeles ; Lillo, M. Pilar ; Sancho, Javier
KeywordsFlavodoxins
Electron transfer proteins
Issue Date17-Aug-2004
PublisherAmerican Society for Biochemistry and Molecular Biology
CitationThe journal of biological chemistry Vol. 279, Issue 45, 47177-47183
AbstractFlavodoxins are well known one-domain / electron-transfer proteins that, according to the presence or absence of a 20-residue loop splitting the fifth -strand of the central -sheet, have been classified in two groups: long and short-chain flavodoxins, respectively. Although the flavodoxins have been extensively used as models to study electron transfer, ligand binding, protein stability and folding issues, the role of the loop has not been investigated. We have constructed two shortened versions of the long-chain Anabaena flavodoxin in which the split -strand has been spliced to remove the original loop. The two variants have been carefully analyzed using various spectroscopic and hydrodynamic criteria, and one of them is clearly well folded, indicating that the long loop is a peripheral element of the structure of long flavodoxins. However, the removal of the loop (which is not in contact with the cofactor in the native structure) markedly decreases the affinity of the apoflavodoxin-FMN complex. This seems related to the fact that, in long flavodoxins, the adjacent tyrosine-bearing FMN binding loop (which is longer and thus more flexible than in short flavodoxins) is stabilized in its competent conformation by interactions with the excised loop. The modest role played by the long loop of long flavodoxins in the structure of these proteins (and in its conformational stability, see López-Llano, J., Maldonado, S., Jain, S., Lostao, A., Godoy-Ruiz, R., Sanchez-Ruiz, Cortijo, M., Fernández-Recio, J., and Sancho, J. (2004) J. Biol. Chem. 279, 47184–47191) opens the possibility that its conservation in so many species is related to a functional role yet to be discovered. In this respect, we discuss the possibility that the long loop is involved in the recognition of some flavodoxin partners. In addition, we report on a structural feature of flavodoxins that could indicate that the short flavodoxins derive from the long ones.
Publisher version (URL)http://dx.doi.org/10.1074/jbc.M405792200
URIhttp://hdl.handle.net/10261/11928
DOI10.1074/jbc.M405792200
ISSN0021-9258
Appears in Collections:(IQFR) Artículos
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