RGD Reference Report - A role for N-myristoylation in protein targeting: NADH-cytochrome b5 reductase requires myristic acid for association with outer mitochondrial but not ER membranes.

General

A role for N-myristoylation in protein targeting: NADH-cytochrome b5 reductase requires myristic acid for association with outer mitochondrial but not ER membranes.
Authors:	Borgese, N Aggujaro, D Carrera, P Pietrini, G Bassetti, M
Citation:	Borgese N, etal., J Cell Biol. 1996 Dec;135(6 Pt 1):1501-13. doi: 10.1083/jcb.135.6.1501.
RGD ID:	153298962
Pubmed:	PMID:8978818 (View Abstract at PubMed)
PMCID:	PMC2133939 (View Article at PubMed Central)
DOI:	DOI:10.1083/jcb.135.6.1501 (Journal Full-text)
N-myristoylation is a cotranslational modification involved in protein-protein interactions as well as in anchoring polypeptides to phospholipid bilayers; however, its role in targeting proteins to specific subcellular compartments has not been clearly defined. The mammalian myristoylated flavoenzyme NADH-cytochrome b5 reductase is integrated into ER and mitochondrial outer membranes via an anchor containing a stretch of 14 uncharged amino acids downstream to the NH2-terminal myristoylate glycine. Since previous studies suggested that the anchoring function could be adequately carried out by the 14 uncharged residues, we investigated a possible role for myristic acid in reductase targeting. The wild type (wt) and a nonmyristoylatable reductase mutant (gly2-->ala) were stably expressed in MDCK cells, and their localization was investigated by immunofluorescence, immuno-EM, and cell fractionation. By all three techniques, the wt protein localized to ER and mitochondria, while the nonmyristoylated mutant was found only on ER membranes. Pulse-chase experiments indicated that this altered steady state distribution was due to the mutant's inability to target to mitochondria, and not to its enhanced instability in that location. Both wt and mutant reductase were resistant to Na2CO3 extraction and partitioned into the detergent phase after treatment of a membrane fraction with Triton X-114, demonstrating that myristic acid is not required for tight anchoring of reductase to membranes. Our results indicate that myristoylated reductase localizes to ER and mitochondria by different mechanisms, and reveal a novel role for myristic acid in protein targeting.

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Cellular Component

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Term	Qualifier	Evidence	With	Reference	Notes	Source	Original Reference(s)
endoplasmic reticulum membrane	located_in	IDA		153298962	PMID:8978818	UniProt
mitochondrial outer membrane	located_in	IDA		153298962	PMID:8978818	UniProt

Molecular Function

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Term	Qualifier	Evidence	With	Reference	Notes	Source	Original Reference(s)
cytochrome-b5 reductase activity, acting on NAD(P)H	enables	IDA		153298962	PMID:8978818	UniProt

Objects Annotated

Genes (Rattus norvegicus)

Cyb5r3 (cytochrome b5 reductase 3)

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A role for N-myristoylation in protein targeting: NADH-cytochrome b5 reductase requires myristic acid for association with outer mitochondrial but not ER membranes.