Table 1. The status of structural features identified to differ between the mammalian closed/active and open/deactive states in preparations of complex I from different species.

	Species	Given name	PDB/EMDB	Resolution (A)	Reference	NDUFA5/10 interface	ND6 TMH3	ND3 TMH1-2 loop	ND1 TMH5-6 loop	ND1 TMH4	NDUFS2 β1–β2 loop	NDUFS7 Arg77 loop
Mammals	Bos taurus	Active-apo	7QSL/14133	2.76	Chung et al. [8]	Extensive	A	A	A	A	A	A
		Deactive-apo	7QSN/14139	2.81	Chung et al. [8]	Restricted	D	D	D	D	D	D
	Mus musculus	Active	6ZR2/11377	3.10	Bridges et al. [9]	Extensive	A	A	A	A	A	A
		ND6-P25L	7AK6/11811	3.82	Yin et al. [10]	Restricted	D	D	D	D	D	D
	Ovis aries	Native-closed	6ZKO/11256	3.80	Kampjut et al. [11]	Extensive	A	A	A	A	A	A
		Native-open1	6ZKP/11257	3.20	Kampjut et al. [11]	Restricted	D	D	D	D	D	D
	Sus scrofa	Active (CIQ)	7V2C/31640	2.90	Gu etal. [12]	Extensive	A	A	A	A	A	A
		Deactive (CIQD)	7V2D/31641	3.30	Gu etal. [12]	Restricted	D	D	D	D	D	D
Plants	Brassica oleracea	Mature	7A23/11614	3.70	Soufari et al. [13]	n/a	D	D	A-like	D-like	Alt	A-like
	Arabidopsis thaliana	Closed	7AR8/11876	3.53	Klusch etal. [14]	n/a	D	D	A-like	D-like	[Alt]	Mixed
		Open	7AR7/11875	3.46	Klusch etal. [14]	n/a	D	D	Alt	D-like	[Alt]	Mixed
Single-cell eukaryotes	Yarrowia lipolytica	n/a	7O71/12742	2.40	Parey et al. [15]	n/a	D	A-like	A-like	D	A	Int
	Tetrahymena thermophila	Closed/Active	7TGH/25882	2.60	Zhou et al. [17]	n/a	A	A	A	A	A	A
Bacteria	Thermus thermophilus	n/a	6Y11/XRC	3.11	Gutierrez et al. [18]	n/a	D	[A-like]	A-like	D-like	Alt	Mixed
	Escherichia coli	Conformation 1	7NYR/12653	3.90	Kolata et al. [19]	n/a	D	D	[Alt]	D	[Alt]	[Mixed]
	Thermosynechococcus vestitus	NDH-1L	6HUM/0281	3.34	Schuller et al. [20]	n/a	D	A-like	A	A	Alt	A
		NDH-1MS	6TJV/10513	3.20	Schuller et al. [21]	n/a	D	A-like	A	A	Alt	A

All the structures listed are ‘as-prepared’ enzymes that have not been treated with substrates, inhibitors or to activate or deactivate them. In S. scrofa and T. thermophila the enzyme is contained in a supercomplex. Each structural feature is compared to its structure defined in this laboratory in the ‘active’ (A) and ‘deactive’ (D) resting states of bovine complex I [8,23,35] and residue numbers are given for the bovine enzyme. Square brackets denote poor density. ND6 TMH3: A, α-helical or D, π-bulge. ND3 TMH1-2, ND1 TMH5-6 and NDUFS2 β1–β2 loops: A, matches the bovine-A loop conformation or A-like, with only minor differences; Alt, in an alternate but ordered conformation; D, disordered. ND1 TMH4: A, bent helix with Y127-Cα in the bovine-A position or A-like, bent helix with Y127-Cα towards the bovine-D position; D-like, straight helix with Y127-Cα toward the bovine-A position or D, straight helix with Y127-Ca in the bovine-D position. NDUFS7 Arg77 loop: A, Arg pointing away from NDUFS2 and an adjacent loop or A-like with the loop retracted; Mixed, state with Arg pointing away from NDUFS2 and an adjacent β-strand; D, Arg pointing towards NDUFS2 and an adjacent β-strand. Note that for A. thaliana the open and closed states correspond to the absence and presence of a domain-bridging ferredoxin supernumerary subunit, respectively, and the closed state does not have the same ordered features as the (mammalian) ‘closed’ state. Note that T. vestitus was previously known as T. elongatus. Abbreviations: n/a, not applicable; XRC, X-ray crystallography.