Dh. Maclennan et al., STRUCTURE-FUNCTION-RELATIONSHIPS IN THE CA2- BINDING AND TRANSLOCATION DOMAIN OF SERCA1 - PHYSIOLOGICAL CORRELATES IN BRODY-DISEASE(), Acta Physiologica Scandinavica, 163, 1998, pp. 55-67
Alanine-scanning mutagenesis of all amino acids in transmembrane helic
es M4, M5, M6 and M8, which contain known Ca2+ binding residues in the
Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum, revealed patch
es of mutation-sensitivity in M4, M5 and M6, but not in M8. A six-resi
due motif, (E/D)GLPA(T/V), in M4 and M6 and its counterpart in M5 were
highlighted by mutagenesis. Site-directed disulfide mapping of helice
s M4 and M6 demonstrated that these transmembrane helices associate as
a right-handed coiled-coil. This structural information, combined wit
h the earlier analysis of the association of each Ca2+ binding residue
with either Ca2+ binding site I or site II, permitted the development
of a ''side-by-side'' model for the two Ca2+ binding sites in the Ca2
+-ATPase. In about half of Brody disease families, mutations create st
op codons which delete all or part of the Ca2+ binding and translocati
on domain, resulting in loss of SERCA1 function and muscle disease.