A nonlinear model of ionic wave propagation along microtubules

Abstract

In our recent paper (SatariT et al. 2009), the Introduction section contained statements regarding the C-terminal tails that have inadvertently been included without properly citing the source of this information provided. In particular, the passage given below should be attributed to Georgiev et al. (2004) who almost 5 years earlier correctly pointed out the importance of the C-terminal tail sequence and structure. "Each tubulin monomer of the MT lattice has a short C-terminal helix H12 followed by a highly acidic amino acid sequence projecting out of the MT outer surface called a tubulin tail (TT). The TTs are short polypeptide sequences of 4-5 nm length when completely outstretched, protruding from the MT surface into the solution. They are essential for MT interactions with MT associated proteins and motor proteins. Jimenez et al. (1999) determined the helicity of a (404-451) and b (394-445) tubulin C-terminal recombinant peptides with the use of NMR spectroscopy. The -tubulin TT amino acid sequence is EEVGADSVEGEGEEEGEEY. The -tubulin tail is 19 amino acids long and possesses 10 negatively charged residues. The situation in the tubulin C-terminal domain is even more interesting. Jimenez et al. found a helix there, which is 9 amino acids longer than in tubulin. This suggests an extension into the protein, supporting the possibility of a functional coil-to-helix transition at the TT zone. The -tubulin TT helix H12 is formed by amino acid residues (408-431) but it seems that the reversible transition between coil and the helix comprising the last 9 amino acid residues (423-431) from -tubulin TT helix (with sequence QQYQDATAD) could either increase or decrease the length of H12, at the same time changing the -TT length.The corresponding residues (432-445) contain the 14 amino acids EQGEFEEEEGEDEA with 9 negatively charged residues (E, A)".The omission of the proper reference and citation has not been intentional on our part but we deeply regret not having given proper care and attention to the source of the statement and wish to apologize to the authors for it. The online version of the original article can be found under References

Lipid body biogenesis and the role of microtubules in lipid synthesis in Ornithogalum umbellatum lipotubuloids

“…Binding [ 3 H]palmitic acid by microtubules is a known method of identification of tubulin palmitoylation (Caron, 1977;Ozols and Caron, 1977;Hemsley et al, 2008). Microtubules might function as electric transmission lines through ionic propagation (Satarić et al, 2009). DGAT1 and DGAT2 present in the vicinity of a lipid body phospholipid monolayer are indispensable in lipid synthesis.…”

How signals of calcium ions initiate the beats of cilia and flagella

“…It has also been explained earlier why the inductance of MTs seen as the transmission line can be safely ignored (15). Based on the experimental findings of Minoura and Muto (22) we estimated the resistivity of an elementary ring to be on the order of 1GΩ: This has been established based on the effective circuit diagram in the context of Kirchhoff's laws constructed for a repetitive arrangement of elementary rings of an MT considered as a ladder-like line, Figure 4.…”

“…Relying on a few experimental assays (21,22), which indicated that the presence of MTs in cytosolic solution increases its ionic conduction, we earlier established an original model which predicts the propagation of signaling ionic impulses along MTs in the form of solitons (15,16,19). We here briefly reexamine this concept in order to apply it for MTs contained in the axoneme of cilia and flagella.…”

“…Above, we have elaborated on three slightly different possible mechanismss involving MTs as nonlinear transmission lines for ionic propagation (15,16,19). The non-linearity originates from nonlinear capacitance of elementary rings, which chiefly arises due to the flexible topology of CTTs.…”

“…This promising scenario relies on the polyelectrolyte properties of constituent microtubules. We previously elaborated (15)(16)(17)(18)(19)(20) on the model of localized ionic pulses propagating along cellular microtubules based on the concept of a nonlinear electric transmission line. The section below describes the following aspects of the subject 1.)…”