A second mammalian N-myristoyltransferase

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Biology

Background:

• N-terminal myristoylation is a crucial cotranslational lipid modification for signaling protein targeting and function.
• N-myristoyltransferase (NMT) catalyzes myristoylation, transferring myristic acid to N-terminal glycine residues.
• Previous research identified one human NMT (hNMT-1), but biochemical evidence suggested multiple NMTs exist in vivo.

Purpose of the Study:

• To clone and characterize a second distinct human NMT, designated hNMT-2.
• To isolate and analyze the mouse homologues for both human NMTs.
• To investigate the functional and molecular differences between hNMT-1 and hNMT-2.

Main Methods:

• Gene cloning and characterization of human and mouse NMTs.
• Transient transfection of NMT cDNAs into COS-7 cells.
• Biochemical assays to measure NMT enzyme activity and substrate selectivity.
• Western blot analysis to examine protein expression and isoform formation.

Main Results:

• A second human NMT, hNMT-2, and its mouse homologue were identified and characterized.
• hNMT-1 and hNMT-2 share high homology with their respective mouse counterparts (>95% amino acid identity) but represent distinct families.
• hNMT-1 produced four distinct protein isoforms, while hNMT-2 appeared as a single 65-kDa protein in transfected cells.
• Both enzymes exhibited similar yet distinguishable substrate selectivities.

Conclusions:

• The human genome encodes at least two distinct NMT enzymes, hNMT-1 and hNMT-2, increasing the known genetic complexity of N-terminal myristoylation.
• The differential expression and isoform formation of NMTs suggest specialized roles in cellular processes.
• Targeting specific NMT enzymes offers a potential strategy for selectively controlling myristoylation-dependent cellular functions.