Table 1. Comparison of sequence identities for the TM4 mutation positions among the 21 human connexin isoforms.

Cx26 amino acid	# of human isoforms for which this amino acid is identical.	Comments
K188	21	E187 also conserved in 21/21 human connexins
F191	20	Exception is L in Cx40.1
M195	17	Conserved β subgroup, except Cx25
A197	8
V198	12
S199	10
G200	5
C202	11	Conserved within β subgroup
I203	17
L205	20	Exception is F in Cx30.2/Cx31.3
N206	15
T208	1	Charged residue position at 209 (E = 20/21; D209 in Cx40.1)

A sequence alignment was performed for 21 human connexins and the TM4 region was examined for residue identity or conservation. The residue number in the left hand column refers to its position in Cx26, however this may not be the same in other connexins because of differences in the sizes of the CL.