Table 1.

Sequence alignment of the putative ligand-binding residues within the nitrate- and bicarbonate-binding proteins

Protein*	Ligand-binding residues†								% identity/% similarity‡
	71	102	155	196	222	239	240	269
NrtA
S. 6803	L	W	Q	H	P	V	G	K	100/100
S. 7942	L	W	Q	H	P	V	G	K	56/72
P. laminosum	P	W	Q	H	P	V	G	K	67/79
T. elongatus	L	W	Q	H	P	V	G	K	66/77
CmpA
S. 6803	I	W	N	Q	P	T	G	E	48/61
S. 7942	I	W	N	Q	S	T	G	E	45/61
T. elongatus	I	W	N	Q	P	T	G	E	48/63
NrtC§
S. 6803	L	W	N	Q	P	V	G	K	33/51
S. 7942	G	W	G	P	P	A	G	K	29/46
P. laminosum	L	W	N	H	P	V	G	K	34/54
T. elongatus	L	W	N	H	P	V	G	K	33/52
CmpC§
S. 6803	L	W	N	H	P	V	S	K	29/49
S. 7942	L	W	N	H	P	I	G	K	29/51
T. elongatus	L	W	N	H	P	V	G	K	30/52

*Protein sequences were from the following cyanobacteria: Synechocystis 6803, Synechococcus 7942, Phormidium laminosum, and Thermosynechococcus elongatus BP-1.

^†Based on overall amino acid sequence alignments by clustalw.

^‡Percent amino acid identity and similarity is given in relation to the Synechocystis 6803 NrtA sequence.

^§Only the last 380 residues were used.