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Tektins are cytoskeletal proteins found in cilia and flagella as structural components of outer doublet microtubules. They are also present in centrioles and basal bodies. They are polymeric in nature, and form filaments.

They include TEKT1, TEKT2, TEKT3, TEKT4, TEKT5.

Structure

Tektin filaments are 2 to 3 nm diameter with two alpha helical segments. They have the consensus amino acid sequence of RPNVELCRD. Different types of tektins, designated as A (53 kDa), B (51 kDa), C (47 kDa) form dimers, trimers and oligomers in various combinations and are also associated with tubulin in the microtubule. Tektins A and B form heteropolymeric protofilaments whereas tektin C forms homodimers. Tektin filaments are present in a supercoiled state. This structure of tektins suggests that they are evolutionarily related to intermediate filaments.

The proteins are predicted to form extended rods composed of 2 alpha- helical segments (~180 residues long) capable of forming coiled coils, interrupted by non-helical linkers. The 2 segments are similar in sequence, indicating a gene duplication event. Along each tektin rod, cysteine residues occur with a periodicity of ~8 nm, coincident with the axial repeat of tubulin dimers in microtubules. It is proposed that the assembly of tektin heteropolymers produces filaments with repeats of 8, 16, 24, 32, 40, 48 and 96 nm, generating the basis for the complex spatial arrangements of axonemal components.

Function

Tektins as integral components of microtubules are essential for their structural integrity. A mutation in the tektin-t genes may lead to defects in flagellar activity which could manifest, for instance, as immotility of sperm leading to male infertility. Tektins are thought to be involved in the assembly of the basal body.

The study of tektins has also been found to be useful in phylogeny, to establish evolutionary relationship between organisms.

Amino acid sequences of tektins are well conserved, with significant similarity between mouse and human homologs.

See also

• Tubulin
• Microtubule

References

1. MA Pirner and RW Linck; Tektins are heterodimeric polymers in flagellar microtubules with axial periodicities matching the tubulin lattice; J. Biol. Chem., Vol. 269, Issue 50, 31800-31806, Dec, 1994
2. Setter PW, Malvey-Dorn E, Steffen W, Stephens RE, Linck RW (September 2006). "Tektin interactions and a model for molecular functions". Exp. Cell Res. 312 (15): 2880–96. doi:10.1016/j.yexcr.2006.05.014. PMID 16831421.
3. Norrander JM, Amos LA, Linck RW (September 1992). "Primary structure of tektin A1: comparison with intermediate-filament proteins and a model for its association with tubulin". Proc. Natl. Acad. Sci. U.S.A. 89 (18): 8567–71. Bibcode:1992PNAS...89.8567N. doi:10.1073/pnas.89.18.8567. PMC 49961. PMID 1528862.
4. ^ Amos LA, Norrander JM, Perrone CA, Linck RW (1996). "Structural comparison of tektins and evidence for their determination of complex spacings in flagellar microtubules". J. Mol. Biol. 257 (2): 385–397. doi:10.1006/jmbi.1996.0170. PMID 8609631.
5. Iguchi N, Tanaka H, Nakamura Y, Nozaki M, Fujiwara T, Nishimune Y (June 2002). "Cloning and characterization of the human tektin-t gene". Mol. Hum. Reprod. 8 (6): 525–30. doi:10.1093/molehr/8.6.525. PMID 12029069.
6. Larsson M, Norrander J, Gräslund S, Brundell E, Linck R, Ståhl S, Höög C (October 2000). "The spatial and temporal expression of Tekt1, a mouse tektin C homologue, during spermatogenesis suggest that it is involved in the development of the sperm tail basal body and axoneme". Eur. J. Cell Biol. 79 (10): 718–25. doi:10.1078/0171-9335-00097. PMID 11089920.
7. Whinnett A, Brower AVZ, Lee M-M, Willmott KR, Mallet J (June 2005). "Phylogenetic Utility of Tektin, a Novel Region for Inferring Systematic Relationships Among Lepidoptera". Annals of the Entomological Society of America. 98 (6): 873–886. doi:10.1603/0013-8746(2005)098[0873:PUOTAN]2.0.CO;2. S2CID 16054233.

• Protein families