High-resolution X-ray crystal structure of cytochrome from porcine liver
Hirano, Yu; Kimura, Shigenobu*; Tamada, Taro
Mammalian microsomal cytochrome (b5) is a hemoprotein which anchored to the membrane of the endoplasmic reticulum and it is involved in various electron transfer reactions, such as lipid unsaturation, cholesterol synthesis and drug metabolism. The 1.5 , structure of b5 from bovine liver reveals that acidic residues located in the vicinity of heme play a role in interaction with electron transfer partners. To further understand the electron transfer mechanism based on the precious structural information, we attempted the structure determination above 1 , resolution of both oxidized (OX) and reduced (RD) form of porcine liver b5. We obtained four types of b5 crystals, OX with/without calcium ion (Ca) and RD with/without Ca, and then collected each dataset above 1 , resolution, 0.85 , (OX + Ca), 0.93 ,(OX - Ca), 0.85 , (RD + Ca), and 0.95 , (RD - Ca). In the both structures of OX and RD form with Ca, two glutamate located in the vicinity of heme participated in the recognition of Ca. From the comparison among four structures, we confirmed that the structural difference between with and without Ca (RMSD: 0.61-0.65 ) is larger than that between OX and RD form (RMSD: 0.12-0.23 ).