, ▁T AP A - 1 ▁( Target ▁of ▁the ▁Ant ip rol ifer ative ▁Ant ib ody ▁ 1 ), ▁and ▁T et ras pan in - 2 8 ▁( T span - 2 8 ). ▁ ▁Gene ▁ ▁The ▁gene ▁is ▁located ▁on ▁the ▁plus ▁str and ▁of ▁the ▁short ▁arm ▁of ▁chrom os ome ▁ 1 1 ▁( 1 1 p 1 5 . 5 ). ▁It ▁is ▁ 2 0 , 1 0 3 ▁bases ▁in ▁length ▁and ▁enc odes ▁a ▁protein ▁of ▁▁ 2 3 6 ▁am ino ▁ac ids ▁( pred icted ▁mole cular ▁weight ▁ 2 5 . 8 0 9 ▁k Da ). ▁ ▁The ▁protein ▁does ▁not ▁appear ▁to ▁be ▁post ▁translation ally ▁modified ▁and ▁has ▁four ▁transm emb rane ▁domains . ▁Both ▁the ▁N - ter minus ▁and ▁C - ter minus ▁lie ▁on ▁the ▁int rac ell ular ▁side ▁of ▁the ▁memb rane . ▁ ▁The ▁gene ▁is ▁expressed ▁in ▁hem opo iet ic , ▁end oth el ial , ▁and ▁ep ith el ial ▁cells . ▁It ▁is ▁absent ▁from ▁er yth ro cy tes , ▁plate lets , ▁and ▁neut roph ils . ▁ ▁Function ▁▁▁ ▁The ▁protein ▁encoded ▁by ▁this ▁gene ▁is ▁a ▁member ▁of ▁the ▁transm emb rane ▁ 4 ▁super family , ▁also ▁known ▁as ▁the ▁t et ras pan in ▁family . ▁Most ▁of ▁these ▁members ▁are ▁cell - sur face ▁prote ins ▁that ▁are ▁character ized ▁by ▁the ▁presence ▁of ▁four ▁hydro ph ob ic