Ca2+ binding effects on the C2 domain conformation of human cytosolic phospholipase A2.
It has been reported that the cooperative binding of calcium ions indicated a local conformational change of the human cytosolic phospholipase A2 (cPLA2) C2 domain (Nalefski et al., (1997) Biochemistry 36, 12011-12018). However its structural evidence is less known (Malmberg et al., (2003) Biochemistry 42, 13227-13240). In this letter, life-time decay and fluorescence quenching techniques were employed to compare the calcium-induced conformational changes. The life-time decay parameters and fluorescence quenching constant changes were small between the apo- and holo-C2 domains when tryptophan residue was excited at 295 nm. In contrast, the quenching constant change was large, from 0.52 M(-1) for the apo-C2 to 8.8 M(-1) for the holo-C2 domain, when tyrosine residues were excited at 284 nm. Our results provide new information on amino acid side chain orientation change at calcium binding loop 3, which is necessary for Ca2+ binding regulated membrane targeting of human cytosolic phospholipase A2.
Tan
Bo
B
Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing, 100101, China.
Qin
San-Bo
SB
Chen
Meng-En
ME
Cang
Huai-Xing
HX
Zhang
Hong-Jie
HJ
D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology*; D006801:Humans; D010741:Phospholipases A / Q000737:chemistry / Q000378:metabolism*; D054467:Phospholipases A2; D011485:Protein Binding; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence
D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium