ISSN:
0886-1544
Keywords:
microtubule structure
;
microtubule assembly
;
electron microscopy of microtubules
;
polymer stabilization
;
microtubule-capping structures
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
Microtubules contain in their lumens distinct structures (plugs) that influence their dynamic behavior in vitro. As observed by electron microscopy, plugs are stainoccluding structures 10-30 nm in length that occur along the lengths and at the ends of microtubules. Plugs occur at a frequency of 20-40% at the ends of microtubules assembled from cycled microtubule protein containing MAPs. While the composition of plugs is not known, preliminary evidence suggests that they are accretions of tubulin, that they are labile, and that they are more common in preparations containing MAPs. When polymers are induced to depolymerize by endwise subuit dissociation, the frequency of plugged microtubule ends increases transiently, suggesting that plugs temporarily stabilize microtubules. The functional significance of plugs may be that they prevent the sudden complete loss of microtubules through catastrophic disassembly. It is possible that plugs, by slowing the rate of disassembly, enable a polymer to add GTP-tubulin subunits, thereby forming a stabilizing GTP-cap. These observations suggest that plugs may stabilize polymers and account for the frequent transitions from shortening to growing phases that characterize dynamic instability.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cm.970150304
Permalink
