Structural insight into the activation mechanism of human pancreatic prophospholipase A2.
Pancreatic phospholipase A2 (phospholipase A2 group 1B, G1B) belongs to the superfamily of secreted phospholipase A2 (PLA2) enzymes. G1B has been proposed to be a potential target for diseases such as hypertension, obesity, and diabetes. Human pancreatic prophospholipase A2 (pro-hG1B) is activated by cleavage of the first seven-residue propeptide (phospholipase A2 propeptide, PROP). However, questions still remain on the mode of action for pro-hG1B. In this work, we expressed pro-hG1B in Pichia pastoris and determined the crystal structure at 1.55-A resolution. The x-ray structure demonstrates that pro-hG1B forms a trimer. In addition, PROP occupies the catalytic cavity and can be self-cleaved at 37 degrees C. A new membrane-bound surface and activation mechanism are proposed based on the trimeric model of pro-hG1B. We also propose a new autoproteolytic mechanism for pro-hG1B by the reaction triad Asp49-Arg0-Ser(-2) that is similar to the serine protease catalytic triad.
Xu
Wei
W
From the Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510663, China; Graduate University of Chinese Academy of Sciences, Beijing 100049, China.
Yi
Lina
L
From the Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510663, China.
Feng
Yumei
Y
From the Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510663, China.
Chen
Ling
L
From the Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510663, China; School of Life Sciences, University of Science and Technology of China, Hefei 230027, China. Electronic address: chen_ling@gibh.ac.cn.
Liu
Jinsong
J
From the Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510663, China; School of Life Sciences, University of Science and Technology of China, Hefei 230027, China. Electronic address: liu_jinsong@gibh.ac.cn.
D000595:Amino Acid Sequence; D002384:Catalysis; D003461:Crystallography; D004789:Enzyme Activation / Q000502:physiology; D054500:Group IB Phospholipases A2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010843:Pichia / Q000235:genetics; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship
D054500:Group IB Phospholipases A2; C516202:PLA2G1B protein, human