» Articles » PMID: 8097117

Site-directed Mutagenesis of Alpha-tubulin. Reductive Methylation Studies of the Lys 394 Region

Overview
Journal Biophys J
Publisher Cell Press
Specialty Biophysics
Date 1993 Mar 1
PMID 8097117
Citations 2
Authors
Affiliations
Soon will be listed here.
Abstract

Previous studies have implicated at least two regions in alpha-tubulin that are important for the regulation of microtubule assembly. These regions include a cluster of basic residues consisting of Arg 390, His 393, and Lys 394 and the highly acidic carboxyl terminus. Lys 394 is highly reactive to HCHO and NaCNBH3. The reductive methylation of Lys 394 by these reagents is thought to be responsible for the profound inhibitory effects of low concentrations of HCHO on microtubule assembly (cf. Szasz J., M. B. Yaffe, M. Elzinga, G. S. Blank, and H. Sternlicht. 1986. Biochemistry. 25:4572-4582). In this study we reexamined the basis for this inhibition. Lys 394 in a human keratinocyte alpha-tubulin (k alpha 1) was replaced by a glutamic acid residue using site-directed mutagenesis. The mutant K394E was synthesized in vitro using rabbit reticulocyte lysates, and its ability to coassemble with bovine brain microtubule protein (MTP) before and after reaction with HCHO and NaCNBH3 was compared with that of wild-type. No differences in the coassemblies of the unmethylated proteins were detected suggesting that Lys 394 is not essential for microtubule assembly. However, methylated K394E prepared at low HCHO concentrations (< 1 mM) incorporated into microtubules to a greater extent (approximately 30-40%) than methylated wild-type. This result is consistent with the hypothesis that methylation of Lys 394 interferes with microtubule assembly. However, the extent of protection afforded by the replacement of Lys 394 with Glu 394 was less than half as large as that predicted from the earlier studies. We tentatively conclude that another residue(s) besides Lys 394 contributes significantly to the assembly-inhibition observed with low concentrations of HCHO. Since this residue(s) is less reactive than Lys 394, it would have to inhibit assembly substoichiometrically when methylated. Potential candidates for this residue include bulk lysyl residue(s), a lysyl residue(s) with intermediate reactivity toward HCHO, and the NH2-termini. The NH2-termini are especially attractive candidates since they appear to have a structural role in microtubule assembly.

Citing Articles

Acetylated α-tubulin K394 regulates microtubule stability to shape the growth of axon terminals.

Saunders H, Johnson-Schlitz D, Jenkins B, Volkert P, Yang S, Wildonger J Curr Biol. 2022; 32(3):614-630.e5.

PMID: 35081332 PMC: 8843987. DOI: 10.1016/j.cub.2021.12.012.


Effects of methionine on the cytoplasmic distribution of actin and tubulin during neural tube closure in rat embryos.

Moephuli S, KLEIN N, Baldwin M, Krider H Proc Natl Acad Sci U S A. 1997; 94(2):543-8.

PMID: 9012820 PMC: 19549. DOI: 10.1073/pnas.94.2.543.

References
1.
Serrano L, Montejo De Garcini E, Hernandez M, Avila J . Localization of the tubulin binding site for tau protein. Eur J Biochem. 1985; 153(3):595-600. DOI: 10.1111/j.1432-1033.1985.tb09342.x. View

2.
Oosawa F, Kasai M . A theory of linear and helical aggregations of macromolecules. J Mol Biol. 1962; 4:10-21. DOI: 10.1016/s0022-2836(62)80112-0. View

3.
Soifer D . Factors regulating the presence of microtubules in cells. Ann N Y Acad Sci. 1986; 466:1-7. DOI: 10.1111/j.1749-6632.1986.tb38378.x. View

4.
Blank G, Yaffe M, Szasz J, George E, Rosenberry T, Sternlicht H . The role of Lys 394 in microtubule assembly. Ann N Y Acad Sci. 1986; 466:467-81. DOI: 10.1111/j.1749-6632.1986.tb38425.x. View

5.
Andreu J, Timasheff S . Tubulin-colchicine interactions and polymerization of the complex. Ann N Y Acad Sci. 1986; 466:676-89. DOI: 10.1111/j.1749-6632.1986.tb38451.x. View