. Author manuscript; available in PMC: 2017 Aug 15.

Published in final edited form as: Arch Biochem Biophys. 2016 Jun 13;604:63–73. doi: 10.1016/j.abb.2016.06.008

Table 1.

Inhibitors of microtubule assembly – effects on the aberrant polymerization reactions induced by (−)-rhazinilam and NSC 613241

Compound	Inhibits (−)-rhazinilam reaction		Inhibits NSC 613241 reaction			Independent aberrant	That confounds interpretation
	At 10 ºC	At 20 ºC	At 0 ºC	At 10 ºC	At 20 ºC	assembly reaction	Of (−)-rhazinilam rxn	Of NSC 613241 rxn
Podophyllotoxin	Yes^a	Yes^a	Yes^a	Yes^a	Yes^a	No	NM^b	NM^b
Thiocolchicine^c	Yes	Yes	Yes	Yes	No	Yes	No	No
Combretastatin A-4	Yes	No	Yes	Yes	No	No	NM^b	NM^b
Nocodazole	Yes	Yes	Yes^a	Yes^a	Yes^a	Yes	No	No
Vinorelbine	Yes^a	Yes^a	Yes^a	Yes^a	Yes^a	No	NM^b	NM^b
Vinblastine	No^d	No^d	Yes	Yes	No	Yes	Yes	No
Vincristine	No^d	No^d	Yes	Yes	No	Yes	Yes	No
Maytansine	Yes^a	Yes^a	Yes^a	Yes^a	Yes^a	No	NM^b	NM^b
Dolastatin 10	Yes	Yes	Yes	Yes	Yes	Yes	No	No
Cryptophycin 1	Yes	Yes	Yes	No	No	No	NM^b	NM^b
Hemiasterlin	Yes^a	Yes^a	Yes^a	Yes^a	Yes^a	No	NM^b	NM^b
Dolastatin 15	Yes	No	Yes	Yes	No	No	NM^b	NM^b
Pentapeptide^e	Yes	Yes	Yes	Yes	Yes	Yes	No	No
Halichondrin B	Yes^a	Yes^a	Yes^a	Yes^a	Yes^a	No	NM^b	NM^b
Spongistatin 1	Yes^a	Yes^a	Yes^a	Yes^a	Yes^a	No	NM^b	NM^b

Complete inhibition (no change in turbidity for 20 min at the indicated temperature).

Not meaningful, since indicated agent caused no aberrant assembly reaction, as indicated by a change in apparent absorption at 350 nm, under the reaction conditions used in the experiment.

Because of the relatively slow, temperature-dependent binding of thiocolchicine to tubulin, thiocolchicine was preincubated with tubulin to form the stable tubulin-thiocolchicine complex. Tubulin at 5.0 mg/mL with 500 μM thiocolchicine was incubated for 1 h at 37 ºC in 1.0 M monosodium glutamate (pH 6.6), 1 mM MgCl₂, 5% dimethyl sulfoxide, and 0.4 mM GTP. The reaction mixture was chilled on ice and frozen in liquid nitrogen. For this experiment, control tubulin was incubated under the same reaction conditions without thiocolchicine (the control tubulin solution became turbid, due to assembly, but reclarified when placed on ice). Both solutions were examined at 1.0 mg/mL tubulin with addition of 10 μM (−)-rhazinilam or 10 μM NSC 613241.

Aberrant assembly reactions induced by vinblastine and vincristine make it difficult or impossible to evaluate potential inhibition of the reactions induced by (−)-rhazinilam and NSC 613241. See the turbidity curves presented in the Supplemental Material.

N,N-dimethylvalyl-valyl-N-methylvalyl-prolyl-proline.