Structural basis of fatty acid activation and transport by human FATP2

Abstract

Fatty acid transport proteins (FATPs) are responsible for efficient uptake of fatty acids (FAs), essential biomolecules that play critical roles in development and growth. However, the lack of three-dimensional structures of FATPs has hindered our understanding of their mechanisms. Here, we report two cryo-EM structures of human FATP2a: wild-type (WT) FATP2a in intermediate state at 2.93 Å and a catalytic mutant of FATP2a in pre-catalytic state at 2.76 Å. In the two structures, both the oleoyl-AMP intermediate and ATP occupy the same central pocket with the acyl group of oleoyl-AMP pointing upwards and placed in a hydrophobic tunnel while the phosphate groups of ATP pointing downwards and interacting with a central loop. The structures also reveal that FAs from the membrane must undergo a two-step translocation to access the catalytic center. The binding of a new FA before the completion of a working cycle may be crucial to ensure the catalytic and transport efficiency. Furthermore, we demonstrate that FATP2a transport FAs, strictly dependent on the activation of FAs through the acyl-CoA synthetase activity. Our findings provide important insights into the working mechanism of FATPs and offer a structural basis for the development of inhibitors targeting FATPs to treat related diseases. Here, the high resolution cryo-EM structures of human FATP2 in both the pre-catalytic and intermediate states, combined with biochemical validations, reveal a catalysis-dependent mechanism for FATP2-mediated fatty acid transport.