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

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Abstract
Uptake and competition experiments were performed with N. 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 .LAMBDA.-cis configuration about the Fe center and 3 identical ornithyl-.delta.-N-acetyl groups as surrounding residues. These ferrichrome-type siderophores are recognized by a common ferrichrome receptor. The ferrichrome receptor is .lambda.-cis specific from the inability to take up the synthetic enantiomers, enantio-ferrichrome and enantio-ferricrocin, possessing a .DELTA.-cis configuration about the Fe center. Coprogen, possessing a .DELTA.-absolute configuration and 2 trans-anhydromevalonic acid residues around the metal center, was also taken up by N. crassa and was competitively inhibited by the ferrichrome-type siderophores. The existence of a common siderophore transport system but the presence of different siderophore receptors in N. crassa, is proposed. 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.