Two equimolar beta chains can be resolved from sea urchin sperm flagellar and scallop gill ciliary tubulins, and from certain brain tubulins as well, using the Triton X-100-acid-urea polyacrylamide gel system commonly used for histone analysis. The beta chains are identified as such from their mobility on urea-free SDS PAGE, from amino acid composition, and from tryptic peptide distribution. Scallop beta chains have almost identical amino acid profiles but they differ by one tryptic peptide. Optimal conditions for beta chain resolution are very species-dependent, with some closely related species showing either maximal or no beta chain separation. In addition, beef brain tubulin on Triton X-100-acid-urea electrophoresis and scallop gill ciliary tubulin upon isoelectric focusing in the presence of SDS show two approximately equimolar alpha chains. These data, indicating equimolar amounts of two potentially different tubulin heterodimers from a variety of microtubule types, support a model for microtubule structure wherein protofilaments consist of alternating heterodimers of two kinds, generating a 16-nm (2-dimer) axial repeat.
Skip Nav Destination
Article| August 01 1982
Equimolar heterodimers in microtubules.
R E Stephens
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1982) 94 (2): 263–270.
R E Stephens; Equimolar heterodimers in microtubules.. J Cell Biol 1 August 1982; 94 (2): 263–270. doi: https://doi.org/10.1083/jcb.94.2.263
Download citation file: