siderophore from Mycobacterium smegmatis
نویسندگان
چکیده
The extracellular siderophore from Mycobacterium smegmatis, exochelin MS, was isolated from iron-deficiently grown cultures and purified to > 98 % by a combination of ion-exchange chromatography and h.p.l.c. The material is unextractable into organic solvents, is basic (pI = 9.3-9.5), has a Amax. at 420 nm and a probable K. for Fe3+ of between 1025 and 1030. Its structure has been determined by examination of desferriand ferriexochelin and its gallium complex. The methods used were electrospray-m.s. and oneand two-dimensional (NOESY, DQFCOSY and TOCSY) 'H n.m.r. The constituent amino acids were examined by chiral g.l.c analysis of N-trifluoroacetyl isopropyl and N-pentafluoropropionyl methyl esters after hydrolysis, and reductive HI hydrolysis, of the siderophore. The exochelin is a formylated pentapeptide: N-(6-N-formyl,fN-hydroxy-Rornithyl)-,/-alaninyl4N-hydroxy-R-ornithinyl-R-allo-threoninyl-
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