Biomedical subjects
Publications and source records attributed to K Taraz.
By comparison of the NMR data of the ferribactins from Pseudomonas chlororaphis ATCC 9446 and of P. fluorescens 18.1 with those of their Ga3+-complexes as models for the Fe3+-complexes it will be shown that only two bidentate ligands are provided for complexation, both located in the peptide chain. The two remaining free sites of the octahedral metal ion are probably occupied by solvent molecules.
From Pseudomonas putida CFML 90-44 an isopyoverdin was isolated. Its structure could be elucidated by chemical degradation and spectroscopic data.
The structures of the pyoverdins isolated from the Pseudomonas spp. 96-312 and 96-318 were elucidated by spectroscopic and degradation techniques. As observed before for Pseudomonas spp. producing pyoverdins with a C-terminal cyclopeptidic substructure, the two strains can recognize to some extent structurally different pyoverdins as long as they have also a similar cyclopeptidic C-terminus.
From seven different pathovars of Pseudomonas syringae representing various genetic subgroups, and one strain of Pseudomonas viridiflava the same pyoverdin siderophore (1) was isolated, probably identical with the pyoverdin whose amino acid composition (but not their sequence) had been reported before. 1 is the first pyoverdin where two of the ligands for Fe3+ are beta-hydroxy Asp units. Its remarkably high complexing constant for Fe3+ at pH 5 as compared with other pyoverdins offers a definite advantage in plant infection. The structure elucidation of 1 will be described and the taxonomical implications regarding pyoverdins with different structures ascribed previously to P. syringae strains will be discussed.
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The structures of two pyoverdins (Pp1 and Pp2) and one dihydropyoverdin (dihydro-Pp2) from a strain of Pseudomonas putida have been elucidated by spectroscopic methods and degradation studies. The pyoverdins Pp1 and Pp2 consist of a chromophore which was identified as (1S)-5-amino-2,3-dihydro-8,9-dihydroxy-1 H-pyrimido[1,2-a]quinoline-1- carboxylic acid substituted at the amino group with a 3-carboxypropanoyl or a succinamoyl residue and at the carboxy group with the N-terminus of L-Ser-L-Thr-D-Ser-L-Orn-L-threo-(OH)Asp-[D-Glu + L-Dab]*-L-Ser-D-allo-Thr- L-c(OH)Orn. Dihydro-Pp2 differs from Pp2 only in the chromophore, which is saturated at carbons 5 and 6. All compounds contain a tetrahydropyrimidine moiety ([D-Gln + L-Dab]*) resulting from the condensation of 2,4-diaminobutyric acid and glutamine.
From a strain of Pseudomonas fluorescens pseudobactin and several related compounds were isolated and their structures were elucidated. In this way a reference compound (5) could be obtained for the unambiguous determination of the absolute configuration of C-1 of the pyoverdin chromophore in newly isolated representatives of this class.
From Pseudomonas aeruginosa three siderophores belonging to the pyoverdine group have been isolated which differ only in the acid side chains bound to the quinoline chromophore.