Protein myristoylation in health and disease

Abstract

N-myristoylation is the attachment of a 14-carbon fatty acid, myristate, onto the N-terminal glycine residue of target proteins, catalysed by N-myristoyltransferase (NMT), a ubiquitous and essential enzyme in eukaryotes. Many of the target proteins of NMT are crucial components of signalling pathways, and myristoylation typically promotes membrane binding that is essential for proper protein localisation or biological function. NMT is a validated therapeutic target in opportunistic infections of humans by fungi or parasitic protozoa. Additionally, NMT is implicated in carcinogenesis, particularly colon cancer, where there is evidence for its upregulation in the early stages of tumour formation. However, the study of myristoylation in all organisms has until recently been hindered by a lack of techniques for detection and identification of myristoylated proteins. Here we introduce the chemistry and biology of N-myristoylation and NMT, and discuss new developments in chemical proteomic technologies that are meeting the challenge of studying this important co-translational modification in living systems.

Fig. 1

a Co-translational and b post-translational myristoylation. MetAP methionine aminopeptidase

Fig. 2

NMT catalytic cycle

Fig. 3

Crystal Structure of NMT and bound myristoyl-CoA (MYA) (PDB: 1IID) showing helical structure in purple, β-sheet in yellow, a peptide substrate in blue, myristate in red and CoA in green. Image generated with PyMol (2008, DeLano Scientific)

Fig. 4

Part of the chemical transformation step. N-terminal peptide glycine (blue) can interact with Tyr3 of the substrate (blue), the enzyme C-terminal carboxylate (Leu455) and other enzyme residues (black). The angle of attack at the myristoyl-CoA thioester (red) is marked as a red line

Fig. 5

Summary of the peptide substrate specificity of ScNMT. Residues are numbered from the leader methionine, which must be removed by methionine aminopeptidase prior to myristoylation

Fig. 6

NMT splice variants

Fig. 7

Regulation of myristoylation in S. cerevisiae. FAA1 is an acyl-CoA synthetase; MetAP methionine aminopeptidase, FA fatty acid

Fig. 8

Two-signal hypothesis of myristate-mediated membrane binding. Myristate (red), palmitate (pink), protein (blue) and membrane-bound protein (green). See text for detail

Fig. 9

Myristoyl switches, A, B and C. Ligands (green); acyl chain (red); protein (blue). See text for detail. D ARF myristoyl switch

Fig. 10

Post-translational myristoylation of Bid during apoptosis

Fig. 11

The involvement of Fus1 in apoptosis

Fig. 12

The three key bioorthogonal ligation reactions in common use in chemical proteomics and protein labelling. A Staudinger-Bertozzi ligation between a phosphine and an organic azide; B Cu(I) catalysed 3+2 cycloaddition reaction between an alkyne and an azide; C strain-promoted 3+2 cycloaddition reaction between a cyclooctyne and an azide. R and R¹ can be any set of labels, proteins, DNA or other biomolecules

Fig. 13

Myristic acid, myristoyl-CoA and analogues

Fig. 14

Example of a tagging by substrate experiment for myristoylation, such as that used by Ploegh and co-workers [141]