Binding sites of calmodulin and actin on the brain spectrin, calspectin.
Open Access
- 1 August 1983
- journal article
- research article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 97 (2), 574-578
- https://doi.org/10.1083/jcb.97.2.574
Abstract
We used rotary-shadowing electron microscopy to map the calmodulin-and actin-binding sites on the brain spectrin, calspectin (or fodrin). Calspectin dimers appeared as rods 110 nm long and joined in a head-to-head manner to form tetramers 220 nm long. We determined calmodulin-binding sites by a ferritin-labeling method combined with biotin-avidin complex formation. Ferritin particles were found to attach to the head parts of calspectin dimers at a position 10-20 nm from the top of the head. The number of the calmodulin-binding sites seemed to be only one for each dimer and two for each tetramer. In contrast, the actin-binding sites were localized at the tail ends of the calspectin molecules. The tetramers attached to muscle F-actin with their tail ends and often cross-linked adjacent filaments. The results are discussed in view of the analogy to the erythrocyte spectrin.Keywords
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