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J. Biol. Chem., Vol. 278, Issue 5, 3089-3097, January 31, 2003

This Article Full Text Full Text (PDF) All Versions of this Article: 278/5/3089    most recent M205853200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ogut, O. Articles by Jin, J.-P. Search for Related Content PubMed PubMed Citation Articles by Ogut, O. Articles by Jin, J.-P. Social Bookmarking                      What's this?

Interactions between Nebulin-like Motifs and Thin Filament Regulatory Proteins^*

Ozgur Ogut, M. Moazzem Hossain, and Jian-Ping Jin

From the Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4970

Nebulin (600-900 kDa) and nebulette (107-109 kDa) are two homologous thin filament-associated proteins in skeletal and cardiac muscles, respectively. Both proteins are capped with a unique region at the amino terminus as well as a serine-rich linker domain and SH3 domains at the COOH terminus. Their significant size difference is attributed to the length of the central region wherein both proteins are primarily composed of ~35 amino acid repeats termed nebulin-like repeats or motifs. These motifs are marked by a conserved SXXXY sequence and high affinity binding to F-actin. To further characterize the effects that nebulin-like proteins may have on the striated muscle thin filament, we have cloned, expressed, and purified a five-motif chicken nebulette fragment and tested its interaction with the thin filament regulatory proteins. Both tropomyosin and troponin T individually bound the nebulette fragment, although the affinity of this interaction was significantly increased when tropomyosin-troponin T was tested as a binary complex. The addition of troponin I to the tropomyosin-troponin T complex decreased the binding to the nebulette fragment, indicating an involvement of the conserved T2 region of troponin T in this interaction. F-actin cosedimentation demonstrated that the nebulette fragment was able to significantly increase the affinity of the tropomyosin-troponin assembly for F-actin. The relationships provide a means for nebulin-like motifs to participate in the allosteric regulation of striated muscle contraction.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank^TM/EBI Data Bank with accession number(s) AF440239.

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