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Identification of the trapped calcium in the gelsolin segment 1—actincomplex: Implications for the role of calcium in the control of gelsolin activity
Author(s) -
Alan G. Weeds,
John Gooch,
Paul McLaughlin,
Brian Pope,
M. Bengtsdotter,
Roger Karlsson
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00109-m
Subject(s) - gelsolin , calcium , chemistry , actin , biophysics , biochemistry , crystallography , biology , organic chemistry
The X‐ray structure of the complex of actin with gelsolin segment 1 revealed the presence of two calcium ions, one bound at an intramolecular site within segment 1 and the other bridging the segment directly to actin. Although earlier calcium binding studies at pH 8.0 revealed only a single calcium trapped in the complex (and also in the binary gelsolin‐actin complex), it is here shown that two calcium ions are bound under the conditions of crystallization at physiological pH. Mutation of acidic residues in either actin or segment 1 involved in ligation of the intermolecular calcium ion resulted in loss of one of the bound calcium ions at pH <7, but not at pH 8. Thus the calcium ion trapped in the segment 1‐actin complex is that located at the intramolecular site. The implications of this for gelsolin function are discussed.