Table 2.

Calcium-coordinating ligands in the pseudo EF-hand (EF1) and canonical EF-hand (EF2) of S100 proteins^a, ^b, ^c

Position (EF1)	1	2	3	4	5	6	7	8	9	10	11	12	13	14
S100B	S	G	R	E	G	D	K	H	K	L	K	K	S	E
S100A1	S	G	K	E	G	D	K	Y	K	L	S	K	K	E
S100A2	S	C	Q	E	G	D	K	F	K	L	S	K	G	E
S100A3	A	G	R	C	G	D	K	Y	K	L	C	Q	A	E
S100A4	S	G	K	E	G	D	K	F	K	L	N	K	S	E
S100A5	S	G	R	E	G	S	K	L	T	L	S	R	K	E
Position (EF2)	1	2	3	4	5	6	7	8	9	10	11	12
S100B	D	N	D	G	D	G	E	C	D	F	Q	E
S100A1	D	E	N	G	D	G	E	V	D	F	Q	E
S100A2	D	E	N	S	D	Q	Q	V	D	F	Q	E
S100A3	D	T	N	K	D	C	E	V	D	F	V	E
S100A4	D	S	N	R	D	N	E	V	D	F	Q	E
S100A5	D	K	N	S	D	Q	E	V	D	F	K	E

^aShown in are the amino acid residues that have their side chain carboxylate oxygen atoms coordinate Ca²⁺ in EF1and EF2.

^bShown in are the amino acid residues that have their backbone carbonyl oxygen atoms coordinate Ca²⁺ in EF1 and EF2.

^cShown in is a water molecule that helps to coordinate calcium in the 9^th position of EF2.