ISSN:
0886-1544
Keywords:
calcium-binding proteins
;
myonemes
;
centrin
;
contractility
;
ciliates
;
protozoa
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
Myonemes are bundles of thin filaments (3-6 nm in diameter) which mediate calcium-induced contraction of the whole or only parts of the cell body in a number of protists. In Eudiplodinium maggii, a rumen ciliate which lacks a uniform ciliation of the cell body, myonemes converge toward the bases of apical ciliary zones that can be retracted under stress conditions, entailing immobilization of the cell. An mAB (A69) has been produced that identifies a calciumbinding protein by immunoblot, immunoprecipitation experiments and specifically labels the myonemes in immunoelectron microscopy. Solubility properties, apparent molecular weight (23 kDa) and isoelectric point (4.9) of the myonemal protein, are similar to the values reported for the calcium-modulated contractile protein centrin. Western-blot analysis indicates that the 23 kDa protein crossreacts antigenically with anti-centrin antibodies. In addition, the 23 kDa protein displays calcium-induced changes in both electrophoretic and chromatographic behaviour, and contains calcium-binding domains that conform to the EF-hand structure, as known for centrin. Based on these observations, we conclude that a calcium-binding protein with major similarities to centrin occurs in the myonemes of E. maggii. We postulate that this protein plays an essential role in myonememediated retraction of the ciliature. © 1994 Wiley-Liss, Inc.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cm.970270208
