Evidence for a common siderophore transport system but different siderophore receptors in Neurospora crassa

Abstract

Uptake and competition experiments were performed with Neurospora crassa and Penicillium parvum by using 14C-labeled coprogen and 55Fe-labeled ferrichrome-type siderophores. Several siderophores of the ferrichrome family, such as ferrichrome, ferricrocin, ferrichrysin, and tetraglycyl-ferrichrome as well as the semisynthetic ferricrocin derivatives O-(phenyl-carbamoyl)-ferricrocin and O-(sulfanilyl-carbamoyl)ferricrocin were taken up by N. crassa. The ferrichrome-type siderophores used vary in the structure of the peptide backbone but possess a common A-cis configuration about the iron center and three identical ornithyl-8-N-acetyl groups as surrounding residues. This suggests that these ferrichrome-type siderophores are recognized by a common ferrichrome receptor. We also concluded that the ferrichrome receptor is X-cis specific from the inability to take up the synthetic enantiomers, enantio-ferrichrome and enantio-ferricrocin, possessing a A-cis configuration about the iron center. On the other hand, we found that coprogen, possessing a A-absolute configuration and two trans-anhydromevalonic acid residues around the metal center, was also taken up by N. crassa and was competitively inhibited by the ferrichrome-type siderophores. We therefore propose the existence of a common siderophore transport system but the presence of different siderophore receptors in N. crassa. In addition, ferrirubin, which is very slowly transported by N. crassa, inhibited both coprogen and ferrichrome-type siderophore transport. Contrary to the findings with N. crassa, transport experiments with P. parvum revealed the presence of a ferrichrome receptor but the absence of a coprogen receptor; coprogen was neither transported nor did it inhibit the ferrichrome transport.

Identification and substrate specificity of a ferrichrome-type siderophore transporter (Arn1p) in Saccharomyces cerevisiae

“…Despite the inability to be recognized by the Arn1 transporter, competition can be observed between structurally‐unrelated siderophores such as ferrirubin and ferrichrysin when tested in the parental strain. We have made similar observations when the simultaneous uptake of coprogen and ferrichromes was studied in N. crassa , suggesting that the loaded transporters compete with one another during passage through the membrane [23,24]. As the siderophore iron transporters of the SIT family turn out to be very specific with regard to the substrates transported, the competition of structurally‐unrelated siderophores may also be interpreted as a downstream effect, which may function inside the cells after transport across the membrane has been completed [10].…”

The pyoverdin receptor FpvA, a TonB-dependent receptor involved in iron uptake byPseudomonas aeruginosa(Review)

“…The specificity for binding to the receptor may be different from the specificity for transport. For example, in the cas e of Neurospor a crassa, the cyclic nature of the peptide is not required for the binding of the iron-coordinated region of the siderophore complex to the receptor, but is necessary for the subs equent transport (Huschka et al 1985, Winkelmann andHuschka, 1987).…”

Utilization of iron-catecholamine complexes involving ferric reductase activity in Listeria monocytogenes

“…Bacteria have developed different systems for iron acquisition (48). The main mechanism consists of the synthesis of Fe(III) chelators, named siderophores, which are low-molecular-weight molecules with high iron affinity secreted by many bacteria (4,22,35; for a review, see reference 37) and fungi (24,26,49) under iron-starved conditions. Phytosiderophore systems have also been described for plants (9,38).…”