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Chromaffin granule membranes contain at least three heme centers: direct evidence from EPR and absorption spectroscopy
Author(s) -
Kamensky Yury A.,
Palmer Graham
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02173-1
Subject(s) - electron paramagnetic resonance , chemistry , heme , absorption spectroscopy , membrane , cytochrome , redox , spectroscopy , photochemistry , hemeprotein , redox titration , analytical chemistry (journal) , crystallography , nuclear magnetic resonance , inorganic chemistry , biochemistry , chromatography , physics , quantum mechanics , enzyme
Low‐temperature electron paramagnetic resonance (EPR) spectroscopy, circular dichroism and two‐component redox titration have previously provided evidence for two different ascorbate‐reducible heme centers in cytochrome b 561 present in chromaffin granule membranes. These species have now been observed by room and liquid nitrogen temperature absorption spectroscopy. The visualization of these heme centers becomes possible as a consequence of utilizing chromaffin granule membranes prepared by a mild procedure. Additionally, a new redox center, not reducible by ascorbate, was discovered by both EPR and absorption spectroscopy. It constitutes about 15% of the heme absorbance of chromaffin membranes at 561 nm and has EPR characteristics of a well‐organized highly axial low‐spin heme center (thus making it unlikely that it is a denatured species). This species is either an alternative form of one of the hemes of cytochrome b 561 that has a very low redox potential or a b ‐type cytochrome distinct from b 561 .