Figure 19-3. Arrangement of protofilaments in singlet, doublet, and triplet microtubules.

Figure 19-3Arrangement of protofilaments in singlet, doublet, and triplet microtubules

In cross section, a typical microtubule, a singlet, is a simple tube built from 13 protofilaments. In a doublet microtubule, an additional set of 10 protofilaments forms a second tubule (B) by fusing to the wall of a singlet (A) microtubule. Attachment of another 10 protofilaments to the B tubule of a doublet microtubule creates a C tubule and a triplet structure.

From: Section 19.1, Microtubule Structures

Cover of Molecular Cell Biology
Molecular Cell Biology. 4th edition.
Lodish H, Berk A, Zipursky SL, et al.
New York: W. H. Freeman; 2000.
Copyright © 2000, W. H. Freeman and Company.

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.