tailieunhanh - Báo cáo khoa học: Dual mitochondrial localization and different roles of the reversible reaction of mammalian ferrochelatase

Ferrochelatase catalyzes the insertion of ferrous ions into protoporphyrin IX to produce heme. Previously, it was found that this enzyme also partici-pates in the reverse reaction of iron removal from heme. To clarify the role of the reverse reaction of ferrochelatase in cells, mouse liver mitochondria were fractionated to examine the localization of ferrochelatase, and it was found that the enzyme localizes not only to the inner membrane, but also to the outer membrane. | Dual mitochondrial localization and different roles of the reversible reaction of mammalian ferrochelatase Masayoshi Sakaino1 Mutsumi Ishigaki1 Yoshiko Ohgari1 Sakihito Kitajima1 Ryuichi Masaki2 Akitsugu Yamamoto3 and Shigeru Taketani1 4 1 Department of Biotechnology Kyoto Institute of Technology Japan 2 The First Department of Physiology Kansai MedicalUniversity Moriguchi Osaka Japan 3 Faculty of Bioscience Nagahama Institute of Bioscience and Technology Nagahama Shiga Japan 4 Insect BiomedicalCenter Kyoto Institute of Technology Japan Keywords ferrochelatase inner membrane iron removal mitochondrialouter membrane phosphorylation Correspondence S. Taketani Department of Biotechnology Kyoto Institute of Technology Sakyo-ku Kyoto 606-8585 Japan Fax 81 75 724 7789 Tel 81 75 724 7789 E-mail taketani@ Received 9 May 2009 revised 18 June 2009 accepted 25 July 2009 doi Ferrochelatase catalyzes the insertion of ferrous ions into protoporphyrin IX to produce heme. Previously it was found that this enzyme also participates in the reverse reaction of iron removal from heme. To clarify the role of the reverse reaction of ferrochelatase in cells mouse liver mitochondria were fractionated to examine the localization of ferrochelatase and it was found that the enzyme localizes not only to the inner membrane but also to the outer membrane. Observations by immunoelectron microscopy confirmed the dual localization of ferrochelatase in ferrochelatase-expressing human embryonic kidney cells and mouse liver mitochondria. The conventional zinc-insertion activities of the enzyme in the inner and outer membranes were similar whereas the iron-removal activity was high in the outer membrane. 2D gel analysis revealed that two types of the enzyme with different isoelectric points were present in mitochondria and the acidic form which was enriched in the outer membrane was found to be phosphorylated. Mutation of human ferrochelatase showed that serine