Table 1 S. pombe tubulin MT polymerisation kinetics MT growth rates were plotted against GTP tubulin concentration for S. pombe single isoform (α1β) and wild type (α1β, α2β) tubulin at 25 °C.

From: Alp7/TACC-Alp14/TOG generates long-lived, fast-growing MTs by an unconventional mechanism

Tubulin isoforms

plus end

minus end

kon nm s−1 μM−1

koff nm s−1

koff/kon μM

kon nm s−1 μM−1

koff nm s−1

koff/kon μM

α1β

3.4

4.1

1.2

1.9

1.7

0.9

α1β, α2β

4.7

9.3

2.0

1.6

3.1

1.9

  1. Apparent rate constants for MT polymerisation were determined by linear regression using a simple polymerisation mechanism where: Growth rate per MT end = kon [tubulin] − koff Units in nm of MT growth are used as the protofilament number is unknown. Assuming 13 or 14 protofilaments conversion factors of 1.62 or 1.75 will convert the values from nm to heterodimers. The critical concentration for MT polymerisation is given by the calculated Kd = koff/kon. The critical concentration is similar at the plus and minus ends in both single and double isoform S. pombe tubulin whilst the rate constants are faster at the plus end.
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