Title: A conserved evolutionary mechanism permits Δ9 desaturation of very-long-chain fatty acyl lipids

Abstract

Δ9 fatty acyl desaturases introduce a cis-double bond between C9 and C10 of saturated fatty acylchains. From the crystal structure of the mouse stearoyl-CoA desaturase (mSCD1) it was proposed that Tyr104, a surface residue, located at the distal end of the fatty acyl binding pocket plays a key role in specifying 18C selectivity. We created mSCD1 Tyr104Gly to test the hypothesis that eliminating this bulky side chain would create an opening and permit the substrate’s methyl end to protrude through the enzyme into the lipid bilayer facilitating the desaturation of very-long-chain (VLC) substrates. Consistent with this hypothesis, Tyr104Gly acquired the ability to desaturate 24C and 26C acyl-CoAs while maintaining its Δ9-regioselectivity. We also investigated two distantly related very-longchain fatty acyl (VLCFA) desaturases from Arabidopsis, ADS1.2 and ADS1.4, which have Ala and Gly, respectively, in place of the gatekeeping Tyr found in mSCD1. Substitution of Tyr for Ala and Gly in ADS1.2 and ADS1.4, respectively, blocked their ability to desaturate VLCFAs. Further, we identified a pair of fungal desaturase homologs, which contained either an Ile or a Gly at this location and showed that only the Gly-containing desaturase was capable of very-long-chain desaturation. The conserved desaturase architecture wherein a surface residuemore » with a single bulky side chain forms the end of the substrate binding cavity predisposes them to single amino acid substitutions that enable a switch between long- and very-long chain selectivity. The data presented here shows that such changes have independently occurred multiple times during the course of evolution.« less

Authors:

Cai, Yuanheng ;

• Search DOE PAGES for author "Cai, Yuanheng"
• Search DOE PAGES for ORCID "0000-0003-3699-3115"

Yu, Xiao-Hong ;

• Search DOE PAGES for author "Yu, Xiao-Hong"
• Search DOE PAGES for ORCID "0000-0003-2352-2023"

Chai, Jin ;

• Search DOE PAGES for author "Chai, Jin"
• Search DOE PAGES for ORCID "0000-0002-4760-5811"

Liu, Chang-Jun ;

• Search DOE PAGES for author "Liu, Chang-Jun"
• Search DOE PAGES for ORCID "0000-0001-6189-8756"

Shanklin, John

• Search DOE PAGES for author "Shanklin, John"
• Search DOE PAGES for ORCID "0000-0002-6774-8043"

Publication Date:

Sat Aug 01 00:00:00 EDT 2020

Research Org.:

Brookhaven National Lab. (BNL), Upton, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1769479

Alternate Identifier(s):

OSTI ID: 1631940

Report Number(s):

BNL-215988-2020-JAAM
Journal ID: ISSN 0021-9258; S0021925817492234; PII: S0021925817492234

Grant/Contract Number:  

SC0012704

Resource Type:

Published Article

Journal Name:

Journal of Biological Chemistry

Additional Journal Information:

Journal Name: Journal of Biological Chemistry Journal Volume: 295 Journal Issue: 32; Journal ID: ISSN 0021-9258

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES