Clostridium MP, flavodoxin

Fio. 6. The hydrogen bonding pattern of the -pleated sheet region in (a) dogfish apo-LDH, (b) lobster holo-GAPDH, (c) horse LADH, (d) adenylate kinase, (e) Clostridium MP flavodoxin, and (f) BPN subtilisin. Residues pointing into the hydrophobic cavities between the sheet and helices have been heavily circled. 

Flavodoxins have a natural spin label, but, unlike the nitroxides, the flavin-free radical suffers from electron de-localisation, which interferes with distance calculations. The broadening of protein resonances in the spectra of the semiquinone forms of flavodoxins from Clostridium MP and Peptostreptococcus elsdenii is highly selective [99], and peaks from groups in the vicinity of the radical can be assigned. 

Brookhaven Protein Databank refcodes 6ACN, Aconitase (Pig) IPHH, p-Hydroxybenzoate hydroxylase (Pseudomonas fluorescens) 3FXN, Flavodoxin (Clostridium MP) 2TS1 Tyrosyl tRNA synthetase (Bacillus stearothermophilus), 2LIV, Leu-Ile-Val binding protein (E. coli). Short format references are given in Appendix B. 

The structure of the FMN-linked electron carrier, flavodoxin, has been determined from Clostridium MP by Ludwig and co-workers 59,60) and the corresponding protein from Desuljovibrio vulgaris by Jensen and coworkers (61). Rao and Rossmann 4) showed that, with the coordinates available to them, the standard deviation, o-, between these two structures this structure can be compared with the AMP mononucleotide binding unit of LDH and found that o- = 2.4 A for 39 equivalent atoms. When was 2.1 A for 102 equivalent Cn atoms. They also showed that part of these two quite different proteins were so aligned, it became clear that FMN binds to flavodoxin at a site similar to where AMP binds to LDH. Not only is it unlikely that this is an accidental structural relationship, but furthermore Baltscheffsky 62) has supported a common evolutionary origin for flavin and NAD+-linked enzymes on the basis of a comparison of their redox potentials. 

Oxidized flavodoxin (Clostridium MP) Semiquinone flavodoxin (Clostridium MP) Adenylate kinase (porcine)... 

---