A covalent linker allows for membrane targeting of an oxylipin biosynthetic complex
A naturally occurring bifunctional protein from Plexaura homomalla links sequential catalytic activities in an oxylipin biosynthetic pathway. The C-terminal lipoxygenase (LOX) portion of the molecule catalyzes the transformation of arachidonic acid (AA) to the corresponding 8R-hydroperoxide, and the N-terminal allene oxide synthase (AOS) domain promotes the conversion of the hydroperoxide intermediate to the product allene oxide (AO). Small-angle X-ray scattering data indicate that in the absence of a covalent linkage the two catalytic domains that transform AA to AO associate to form a complex that recapitulates the structure of the bifunctional protein. The SAXS data also support a model for LOX and AOS domain orientation in the fusion protein inferred from a low-resolution crystal structure. However, results of membrane binding experiments indicate that covalent linkage of the domains is required for Ca2+-dependent membrane targeting of the sequential activities, despite the noncovalent domain association. Furthermore, membrane targeting is accompanied by a conformational change as monitored by specific proteolysis of the linker that joins the AOS and LOX domains. Our data are consistent with a model in which Ca2+-dependent membrane binding relieves the noncovalent interactions between the AOS and LOX domains and suggests that the C2-like domain of LOX mediates both protein-protein and protein-membrane interactions. © 2008 American Chemical Society.
Publication Source (Journal or Book title)
Gilbert, N., Niebuhr, M., Tsuruta, H., Bordelon, T., Ridderbusch, O., Dassey, A., Brash, A., Bartlett, S., & Newcomer, M. (2008). A covalent linker allows for membrane targeting of an oxylipin biosynthetic complex. Biochemistry, 47 (40), 10665-10676. https://doi.org/10.1021/bi800751p