Monday, August 2, 2010
Pacific Concourse (Hyatt Regency San Francisco)
We have extensively studied the biological metabolism of toxic compounds, nitriles*. Rhodococcus rhodochrous J1 produces high- and low-molecular-mass nitrile hydratases (H-NHase and L-NHase), depending on the inducer. The incorporation of cobalt into L-NHase has been found to depend on the α-subunit exchange between cobalt-free L-NHase (apo-L-NHase) and its cobalt-containing mediator, NhlAE (holo-NhlAE), this novel mode of post-translational maturation having been named self-subunit swapping, and NhlE having been recognized as a self-subunit swapping chaperone**.
We here discovered an H-NHase maturation mediator, NhhAG, consisting of NhhG and the α-subunit of H-NHase. The incorporation of cobalt into H-NHase was confirmed to be dependent on self-subunit swapping. For the first time, larger sized particles than apo-H-NHase were observed during the swapping process on dynamic light scattering measurement, suggesting the formation of intermediate complexes. Based upon these findings, we initially proposed a possible mechanism for self-subunit swapping. EPR analysis demonstrated that the coordination environment of a cobalt ion in holo-NhhAG is subtly different from that in H-NHase. Cobalt is inserted into cobalt-free NhhAG (apo-NhhAG) but not into apo-H-NHase, suggesting that NhhG functions not only as a self-subunit swapping chaperone but also as a metallochaperone.
*Nature Biotechnol., 16, 733 (1998); **Proc. Natl. Acad. Sci. USA, 105, 14849 (2008)
We here discovered an H-NHase maturation mediator, NhhAG, consisting of NhhG and the α-subunit of H-NHase. The incorporation of cobalt into H-NHase was confirmed to be dependent on self-subunit swapping. For the first time, larger sized particles than apo-H-NHase were observed during the swapping process on dynamic light scattering measurement, suggesting the formation of intermediate complexes. Based upon these findings, we initially proposed a possible mechanism for self-subunit swapping. EPR analysis demonstrated that the coordination environment of a cobalt ion in holo-NhhAG is subtly different from that in H-NHase. Cobalt is inserted into cobalt-free NhhAG (apo-NhhAG) but not into apo-H-NHase, suggesting that NhhG functions not only as a self-subunit swapping chaperone but also as a metallochaperone.
*Nature Biotechnol., 16, 733 (1998); **Proc. Natl. Acad. Sci. USA, 105, 14849 (2008)