GDGT cyclization proteins identify the dominant archaeal sources of tetraether lipids in the ocean
[1];
[4];
[5];
[1]
- Stanford Univ., CA (United States)
- Univ. of Oklahoma, Norman, OK (United States)
- Univ. of Illinois at Urbana-Champaign, IL (United States)
- Univ. of Illinois at Urbana-Champaign, IL (United States). Inst. for Genomic Biology
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Glycerol dibiphytanyl glycerol tetraethers (GDGTs) are distinctive archaeal membrane-spanning lipids with up to eight cyclopentane rings and/or one cyclohexane ring. The number of rings added to the GDGT core structure can vary as a function of environmental conditions, such as changes in growth temperature. This physiological response enables cyclic GDGTs preserved in sediments to be employed as proxies for reconstructing past global and regional temperatures and to provide fundamental insights into ancient climate variability. Yet, confidence in GDGT-based paleotemperature proxies is hindered by uncertainty concerning the archaeal communities contributing to GDGT pools in modern environments and ambiguity in the environmental and physiological factors that affect GDGT cyclization in extant archaea. To properly constrain these uncertainties, a comprehensive understanding of GDGT biosynthesis is required. Here in this paper, we identify 2 GDGT ring synthases, GrsA and GrsB, essential for GDGT ring formation in Sulfolobus acidocaldarius. Both proteins are radical S-adenosylmethionine proteins, indicating that GDGT cyclization occurs through a free radical mechanism. In addition, we demonstrate that GrsA introduces rings specifically at the C-7 position of the core GDGT lipid, while GrsB cyclizes at the C-3 position, suggesting that cyclization patterns are differentially controlled by 2 separate enzymes and potentially influenced by distinct environmental factors. Finally, phylogenetic analyses of the Grs proteins reveal that marine Thaumarchaeota, and not Euryarchaeota, are the dominant source of cyclized GDGTs in open ocean settings, addressing a major source of uncertainty in GDGT-based paleotemperature proxy applications.
- Research Organization:
- Univ. of Illinois at Urbana-Champaign, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division; National Science Foundation (NSF); Simons Collaboration on the Origins of Life (SCOL)
- Grant/Contract Number:
- FG02-02ER15296; 511568; 1752564
- OSTI ID:
- 1569769
- Alternate ID(s):
- OSTI ID: 1595769
- Journal Information:
- Proceedings of the National Academy of Sciences of the United States of America, Vol. 116, Issue 45; ISSN 0027-8424
- Publisher:
- National Academy of SciencesCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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journal | November 2014 |
Energy flux controls tetraether lipid cyclization in Sulfolobus acidocaldarius
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journal | November 2019 |
The absence of intact polar lipid-derived GDGTs in marine waters dominated by Marine Group II: Implications for lipid biosynthesis in Archaea
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journal | January 2020 |
The absence of intact polar lipid-derived GDGTs in marine waters dominated by Marine Group II: Implications for lipid biosynthesis in Archaea
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journal | January 2020 |
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