ACBD6 protein controls acyl chain availability and specificity of the N-myristoylation modification of proteins

Abstract

of pathogens such as parasitic protozoa, fungi, and viruses (5-12). N-Myristoylation is a multistep process initiated by the binding of myristoyl-CoA to the N-terminal domain of apo-NMT, covalent linkage of the myristoyl chain to the glycine residue, and release of CoA, followed by the final release of the acyl peptide. In retinal photoreceptor cells, C 14:1 and C 14:2 rather than C 14:0 are the fatty acids used to modify proteins such as the -subunit of the G-protein photoreceptor (13-15). While the 14-carbon chain is the preferred substrate, NMT proteins lack binding specificity for C 14-CoA. This renders NMT incapable of preventing the unwarranted occupation of the site by acyl-CoA species other than C 14-CoA (4-6, 10, 13). Because the transfer rate of acyl chains with a length other than C 14 is extremely slow, binding of the "wrong" acyl-CoA blocks the myristoyltransferase cycle for NMT enzymes. In the cell, the greater abundance of acyl-CoAs such as C 16-CoA compared with C 14-CoA would therefore prevent protein myristoylation. It follows that mechanisms that prevent binding or trigger the release of these nontransferable competitors from the myristoyl-CoA binding site are essential in supporting NMT enzyme activity. Acyl-CoA binding domain-containing (ACBD) proteins are involved in the maintenance of diverse cellular functions. They interact with a multitude of proteins and can be located in the cytosol, organelles, or nucleus; bound to membranes; or secreted (16, 17). This protein family regulates processes as diverse as neural stem-cell self-renewal, protein and lipid acylation, lipid homeostasis, intracellular vesicle trafficking, organelle formation, viral replication, and apoptotic response (18-35). Plant ACBD proteins are also implicated in essential functions such as embryogenesis and resistance to various stresses (36-38). Acyl-CoAs

Requirement of the acyl-CoA carrier ACBD6 in myristoylation of proteins: Activation by ligand binding and protein interaction

“…The constructs were cloned in pET28a vector and produced with a carboxyl-terminal hexahistidine tag, as previously described [30]. Details of the various truncations and chimeras are presented in Fig 1.…”

“…After electrophoresis, protein bands were detected with the Gelcode Blue dye. Myristoyltransferase reaction conditions are indicated in the legend of the figures and were performed as previously described [30]. Detection and quantification of the formation of the acyl-peptide in the presence of acyl-CoAs and the peptide GLYVSRLF was performed by reverse phase HPLC [30].…”

“…In the absence of a mechanism protecting NMT from competitive inhibition, the greater abundance of other acyl-CoA, such as C 16 -CoA, would prevent access of the substrate. The human acyl-CoA binding protein ACBD6 interacts with the human (NMT1 and NMT2) and the protozoan Plasmodium falciparum NMT enzymes and, protects their activity [29,30]. The P. falciparum ACBD6 protein also regulates activity of PfNMT [30].…”

“…The human acyl-CoA binding protein ACBD6 interacts with the human (NMT1 and NMT2) and the protozoan Plasmodium falciparum NMT enzymes and, protects their activity [29,30]. The P. falciparum ACBD6 protein also regulates activity of PfNMT [30]. In the NMT2 / ACBD6 complex, the acyl-CoA carrier allows C 14 -CoA to reach NMT binding site, even in the presence of excess concentration of C 16 -CoA and C 12 -CoA [29,30].…”

“…The P. falciparum ACBD6 protein also regulates activity of PfNMT [30]. In the NMT2 / ACBD6 complex, the acyl-CoA carrier allows C 14 -CoA to reach NMT binding site, even in the presence of excess concentration of C 16 -CoA and C 12 -CoA [29,30]. The binding activity and the NMT-stimulatory properties of the acyl-CoA binding (ACB) domain and of the ANK-repeat motifs (ANK module) of ACBD6 were determined in this study.…”