Abstract
A rotary motor in a termite flagellate continually turns the anterior part of the cell (head) in a clockwise direction. Previous descriptive observations implicated the noncontractile axostyle, which runs through the cell like a drive shaft, in the motile mechanism. This study demonstrates directly that the axostyle complex generates torque, and describes serval of its dynamic properties. By laser microbeam irradiation, the axostyle is broken into an anterior segment attached to the cell's head, and a posterior segment which projects caudally as a thin spike, or axostylar projection. Before lasing, both head and axostylar projection rotate at the same speed. After breaking the axostyle, the rotation velocity of the head decreases, depending on the length of the anterior segment. Head speed is not a linear function of axostyle length, however. In contrast, the rotation velocity of the axostylar projection always increases about 1.5 times after lasing, regardless of the length of the posterior segment. Turning the head is thus a load on the axostylar rotary motor, but the speed of the posterior segment represents the free-running motor. A third, middle segment of the axostyle, not connected to the head or axostylar projection, can also rotate independently. No ultrastructural differences were found along the length of the axostyle complex, except at the very anterior end; lenth-velocity data suggest that this region may not be able to generate torque. An electric model of the axostylar rotary motor is presented to help understand the length-velocity data.
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Selected References
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- Amos W. B. Contraction and calcium binding in the vorticellid ciliates. Soc Gen Physiol Ser. 1975;30:411–436. [PubMed] [Google Scholar]
- Berg H. C. Bacterial behaviour. Nature. 1975 Apr 3;254(5499):389–392. doi: 10.1038/254389a0. [DOI] [PubMed] [Google Scholar]
- Berg H. C. Dynamic properties of bacterial flagellar motors. Nature. 1974 May 3;249(452):77–79. doi: 10.1038/249077a0. [DOI] [PubMed] [Google Scholar]
- Cachon J., Cachon M., Tilney L. G., Tilney M. S. Movement generated by interactions between the dense material at the ends of microtubles and non-actin-containing microfilaments in Sticholonche zanclea. J Cell Biol. 1977 Feb;72(2):314–338. doi: 10.1083/jcb.72.2.314. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Larsen S. H., Adler J., Gargus J. J., Hogg R. W. Chemomechanical coupling without ATP: the source of energy for motility and chemotaxis in bacteria. Proc Natl Acad Sci U S A. 1974 Apr;71(4):1239–1243. doi: 10.1073/pnas.71.4.1239. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mooseker M. S., Tilney L. G. Isolation and reactivation of the axostyle. Evidence for a dynein-like ATPase in the axostyle. J Cell Biol. 1973 Jan;56(1):13–26. doi: 10.1083/jcb.56.1.13. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pollard T. D., Weihing R. R. Actin and myosin and cell movement. CRC Crit Rev Biochem. 1974 Jan;2(1):1–65. doi: 10.3109/10409237409105443. [DOI] [PubMed] [Google Scholar]
- Sale W. S., Satir P. Direction of active sliding of microtubules in Tetrahymena cilia. Proc Natl Acad Sci U S A. 1977 May;74(5):2045–2049. doi: 10.1073/pnas.74.5.2045. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Summers K. E., Gibbons I. R. Adenosine triphosphate-induced sliding of tubules in trypsin-treated flagella of sea-urchin sperm. Proc Natl Acad Sci U S A. 1971 Dec;68(12):3092–3096. doi: 10.1073/pnas.68.12.3092. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tamm S. L., Tamm S. Direct evidence for fluid membranes. Proc Natl Acad Sci U S A. 1974 Nov;71(11):4589–4593. doi: 10.1073/pnas.71.11.4589. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tamm S. L., Tamm S. Rotary movements and fluid membranes in termite flagellates. J Cell Sci. 1976 May;20(3):619–638. doi: 10.1242/jcs.20.3.619. [DOI] [PubMed] [Google Scholar]