Rhodotorulic acids

Liu A, Neilands JB (1984) Mutational Analysis of Rhodotorulic Acid Synthesis in Rhodotorula philimanae. 58 97-106 Livage J, see Henry M (1991) 77 153-206... 

The po.ssible role of a chelate reductase for iron uptake from microbial siderophores has been examined for several plant species (30,47). With certain microbial siderophores such as rhizoferrin and rhodotorulic acid, the reductase may easily cleave iron from the siderophore to allow subsequent uptake by the ferrous iron transporter. However, with the hydroxamate siderophore, ferrioxamine B, which is produced by actinomycetes and u.sed by diverse bacteria and fungi, it has been shown that the iron stress-regulated reductase is not capable... 

Rhodotorulic acid Hydroxamic acid 2 Species of Rhodotorula, Sporo-bolomyces, Sporidiobolus, Leuco-sporidium and Rhodosporidium... 

Synthetic linear dihydroxamic acids may be considered as models of rhodotorulic acid (3) to investigate steric effects on the formation of mono- or di-iron(III) species (127,128). pH-dependent electrospray ionization-mass spectrometry (ESI-MS) methods show that ferric complexes with dihydroxamates with short linker chains (37 and 38 in Fig. 15) will prefer the dimeric... 

Fig. 19. Plot of redox potentials (Ey2) as a function of pFe3+ values for a series of hexadentate, tetradentate, and bidentate hydroxamic acid siderophores and siderophore mimics. Data from Table V. Legend 1 — ferrioxamine E 2 — ferrioxamine B (4) 3 — H.aLjf4 (11) 4 — H >L 36 (12) 5 - coprogen 6 - ferricrocin 7 - ferrichrome (6) 8 - alcaligin 9 -rhodotorulic acid (3) 10 — NMAHA 11 — AHA 12 — Ly-AHA.

As mentioned above, transport of siderophores across the cytoplasmic membrane is less specific than the translocation through the outer membrane. In E. coli three different outer membrane proteins (among them FepA the receptor for enterobactin produced by most E. coli strains) recognise siderophores of the catechol type (enterobactin and structurally related compounds), while only one ABC system is needed for the passage into the cytosol. Likewise, OM receptors FhuA, FhuE, and Iut are needed to transport a number of different ferric hydroxamates, whereas the FhuBCD proteins accept a variety of hydroxamate type ligands such as albomycin, ferrichrome, coprogen, aerobactin, shizokinen, rhodotorulic acid, and ferrioxamine B [165,171], For the vast majority of systems, the substrate specificity has not been elucidated, but it can be assumed that many siderophore ABC permeases might be able to transport several different but structurally related substrates. 

Evidence of interactions of actinides with rhodotorulic acid and 2,3-dihydroxy-benzoyl-N-glycine is presented in Figs. 1 and 2. In Fig. la the distribution of plutonium between citric acid, fractions 22—28, and transferrin, fraction 14-18, (the evi-... 

Fig. l.a. Plutonium nitrate in 0.01M HNO3 was passed through a 25 nm membrane, 50 jil of the resulting solution was added to rat serum (1.5 ml) which contained dimethylsulphoxide (75 ii ). The solution was eluted from Sephadex G-25 (0.9 x 60 cm) with 0.1M 2-amino-2-hydroxymethyl-propane-l,2-diol/lM NaCl, pH 8.0. b. The above procedure was repeated with rat serum adjusted to contain 0.01M rhodotorulic acid, added as a dimethylsulphoxide solution, 75 til... 

The structure of rhodotorulic acid, 2,3-dihydroxybenzoyl and two complexing agents produced by lichens are presented in Fig. 3. 

The author is indebted to Professor J.B. Neilands for the gift of rhodotorulic acid and for drawing the author s attention to some references included in this report. 

Atkin CL, Neilands JB (1968) Rhodotorulic Acid, a Diketopiperazine Dihydroxamic Acid with Growth-Factor Activity. I. Isolation and Characterization. Biochemistry 7 3734... 

Carrano CJ, Raymond KN (1978) Coordination Chemistry of Microbial Iron Transport Compounds. 10. Characterization of the Complexes of Rhodotorulic Acid, a Dihydroxa-mate Siderophore. J Am Chem Soc 100 5371... 

The first example of a helical complex with pre-determined chirality was the dinuclear complex [Fe2(rdt)3], where rdtFl2 is the fungal iron chelator rhodotorulic acid, (15), a dihydroxamate siderophore. Several more helical and chiral Fe " " and Fe complexes are documented in the diimine and in the hydroxamate and catechol sections. A doubly looped ( bow tie ) complex has been constructed with the aid of a tris-terimine ligand (Section 5.4.3.5.7). 

Liu, A., NeUands, J. B. Mutational Analysis of Rhodotorulic Acid Sjmthesis in Rhodotorula pilimanae. Vol. 58, pp. 97-106. 

Chromium(III) complexes of a number of polyhydroxamic acids, microbial iron sequestering and transport agents (siderochromes) have been reported.797,798 The kinetic inertness of the chromium(III) complexes allows the facile separation of isomers for the model complex tris(iV-methyl-( - )-methoxyacetylhydroxamato)chromium(III), D-cis, L-cis and the l/d-trans isomers have been separated.798 The chromium complexes of desferrioxamine B (191) have been investigated the possible isomers are illustrated below (192-196). The cis isomer was isolated in relatively pure form.799 Thiohydroxamate800 and dihydroxamate (rhodotorulic acid) complexes have also been studied.801... 

The fundamental structural unit of the ferrichromes, N -hydroxyomithine, is also present in rhodotorulic acid (and related compounds), the fusarinines (Ns-acyl-Ns-hydroxyornithine) and in neurosporin. The diversity of structure and biological activity of these siderophores results from the various substituents present in the peptide and acyl groups. The hydroxamate siderophores are better characterized from a structural viewpoint. X-ray diffraction data are available for the... 

The transport or release of iron has been much discussed. One view is that the iron is transferred from the siderophore complex at the outer membrane to another membrane-bound protein, for example in the uptake of iron by rhodotorulic acid in Rhodotorula. The other view is that the intact Fein-siderophore complex is taken up into the cell. This is supported by studies with inert chromium(III) complexes in E. coli and also by labelling studies. 

---