Abstract

To identify physiologically important human N-myristoylated proteins, 90 cDNA clones predicted to encode human N-myristoylated proteins were selected from a human cDNA resource (4,369 Kazusa ORFeome project human cDNA clones) by two bioinformatic N-myristoylation prediction systems, NMT-The MYR Predictor and Myristoylator. After database searches to exclude known human N-myristoylated proteins, 37 cDNA clones were selected as potential human N-myristoylated proteins. The susceptibility of these cDNA clones to protein N-myristoylation was first evaluated using fusion proteins in which the N-terminal ten amino acid residues were fused to an epitope-tagged model protein. Then, protein N-myristoylation of the gene products of full-length cDNAs was evaluated by metabolic labeling experiments both in an insect cell-free protein synthesis system and in transfected human cells. As a result, the products of 13 cDNA clones (FBXL7, PPM1B, SAMM50, PLEKHN, AIFM3, C22orf42, STK32A, FAM131C, DRICH1, MCC1, HID1, P2RX5, STK32B) were found to be human N-myristoylated proteins. Analysis of the role of protein N-myristoylation on the intracellular localization of SAMM50, a mitochondrial outer membrane protein, revealed that protein N-myristoylation was required for proper targeting of SAMM50 to mitochondria. Thus, the strategy used in this study is useful for the identification of physiologically important human N-myristoylated proteins from human cDNA resources.

Highlights

  • Protein N-myristoylation is the attachment of myristic acid, a 14-carbon saturated fatty acid, to the N-terminal Gly of proteins [1,2,3,4,5]

  • In order to search for human N-myristoylated proteins, 339 cDNA clones with N-terminal Met-Gly motifs were extracted from 4,369 KOP (Kazusa ORFeome project) human cDNA clones (FXC01948 ~ FXC23818) (Fig 1A)

  • After applying the N-terminal sequence of the products of these 339 cDNA clones to two protein N-myristoylation prediction programs, The MYR Predictor and Myristoylator, 90 positively selected cDNA clones were indentified (S3 Table). From these cDNA clones, 53 clones coding for known N-myristoylated proteins identified by database searches were removed, and 37 cDNA clones were selected as potential candidates for human N-myristoylated proteins (Fig 1A)

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Summary

Introduction

Protein N-myristoylation is the attachment of myristic acid, a 14-carbon saturated fatty acid, to the N-terminal Gly of proteins [1,2,3,4,5]. This modification is one of the major forms of lipid modification that occurs on eukaryotic and viral proteins. PLOS ONE | DOI:10.1371/journal.pone.0136360 August 26, 2015

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