W. Xie et al., 2 BASIC-AMINO-ACIDS IN THE 2ND INNER LOOP OF THE INTERLEUKIN-8 RECEPTOR ARE ESSENTIAL FOR G-ALPHA-16 COUPLING, The Journal of biological chemistry, 272(40), 1997, pp. 24948-24951
The involvement of basic residues of interleukin (IL)-8 receptors in c
oupling to the Gi and G16 proteins was investigated by using a series
of IL-8 receptor mutants, Substitution of the basic amino acids in the
third inner loop of the receptor does not alter the abilities of the
receptor mutants to activate recombinant G alpha 16 or phosphoinositid
e-specific phospholipase C (PLC) beta 2 expressed in COS-7 cells. Howe
ver, an IL-8 receptor mutant with double mutations at residues Lys(158
) and Arg(159) of the second inner loop loses its abilities to activat
e G alpha 16 but retains its ability to activate PLC beta 2. The activ
ation of PLC beta 2 by an IL-8 receptor that is sensitive to pertussis
toxin has been previously demonstrated to be mediated through G beta
gamma. Surprisingly, the IL-8 receptor mutants with substitution of Al
a for either residue Lys(158) or Arg(159) can still activate G alpha 1
6, which suggests that either of the two basic residues in the second
inner loop of the IL-8 receptor is sufficient for G alpha 16 coupling.