Document Type

Article

Language

eng

Publication Date

1-15-2017

Publisher

Portland Press Limited

Source Publication

Biochemical Journal

Source ISSN

1470-8728

Original Item ID

DOI: 10.1042/BCJ20160884

Abstract

The Fe-type nitrile hydratase activator protein from Rhodococcus equi TG328-2 (ReNHase TG328-2) was successfully expressed and purified. Sequence analysis and homology modeling suggest that it is a G3E P-loop guanosine triphosphatase (GTPase) within the COG0523 subfamily. Kinetic studies revealed that the Fe-type activator protein is capable of hydrolyzing GTP to GDP with a kcat value of 1.2 × 10−3 s−1 and a Km value of 40 μM in the presence of 5 mM MgCl2 in 50 mM 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid at a pH of 8.0. The addition of divalent metal ions, such as Co(II), which binds to the ReNHase TG328-2 activator protein with a Kd of 2.9 μM, accelerated the rate of GTP hydrolysis, suggesting that GTP hydrolysis is potentially connected to the proposed metal chaperone function of the ReNHase TG328-2 activator protein. Circular dichroism data reveal a significant conformational change upon the addition of GTP, which may be linked to the interconnectivity of the cofactor binding sites, resulting in an activator protein that can be recognized and can bind to the NHase α-subunit. A combination of these data establishes, for the first time, that the ReNHase TG328-2 activator protein falls into the COG0523 subfamily of G3E P-loop GTPases, many of which play a role in metal homeostasis processes.

Comments

Accepted version. Biochemical Journal, Vol 474, No. 2 (January 15, 2017): pg. 247-258. DOI. © 2017 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society. Used with permission.

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