The high-resolution crystal structure of human LCAT.
(2015) J Lipid Res 56: 1711-1719
Authors: Piper, D.E., Romanow, W.G., Gunawardane, R.N., Fordstrom, P., Masterman, S., Pan, O., Thibault, S.T., Zhang, R., Meininger, D., Schwarz, M., Wang, Z., King, C., Zhou, M., Walker, N.P.
Abstract
LCAT is intimately involved in HDL maturation and is a key component of the reverse cholesterol transport (RCT) pathway which removes excess cholesterol molecules from the peripheral tissues to the liver for excretion. Patients with loss-of-function LCAT mutations exhibit low levels of HDL cholesterol and corneal opacity. Here we report the 2.65 ? crystal structure of the human LCAT protein. Crystallization required enzymatic removal of N-linked glycans and complex formation with a Fab fragment from a tool antibody. The crystal structure reveals that LCAT has an α/β hydrolase core with two additional subdomains that play important roles in LCAT function. Subdomain 1 contains the region of LCAT shown to be required for interfacial activation, while subdomain 2 contains the lid and amino acids that shape the substrate binding pocket. Mapping the naturally occurring mutations onto the structure provides insight into how they may affect LCAT enzymatic activity.