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tektin
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.〔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〕
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.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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