Table 2.

Heme Protein Database midpoint potential statistics^a

	Entries	Range	Average	Median
Heme domain CATH class
All (1–4)	153	−550 to +450	−14.6	−6
Mainly alpha (1)	99	−412 to +450	44.6	47
Mainly beta (2)	10	−303 to +373	9.1	32.5
Mixed alpha/beta (3)	32	−550 to +68	−207.5	−237.5
Low 2° structure (4)	2	−172 to −25	−98.5	−98.5
Heme type
Heme a	4	+221 to +290	254.25	253
Heme b	42	−550 to +250	−46.1	−4.5
Heme c	102	−412 to +450	−12.8	−31
Heme d1	1	287	287	287
Heme o	1	160	160	160
siroheme	1	−340	−340	−340
P460	1	−260	−260	−260
Fe(coproporphyrin)	1	140	140	140
Heme coordination motif
All	153	−550 to +450	−20.4	−10
His/His	69	−412 to +380	−132.2	−177
His/Met	36	−60 to +450	242.1	263.5
His/Tyr	1	−550	−550	−550
His/NTerm	3	−260 to +373	156	355
His/OH	1	287	287	287
His/Asn	1	−22	−22	−22
Met/Met	1	140	140	140
Cys/–	9	−340 to −6	−244.6	−295
His/–	28	−306 to +290	10	49
Lys/–	1	−107	−107	−107
Tyr/–	1	−303	−303	−303
−/–	1	100	100	100

^aAll potentials reported in mV versus SHE.