Distinct association of HRAS and KRAS with Mn(II) ion illustrated by paramagnetic NMR

<p><a name="OLE_LINK4"></a><span>RAS proteins are among crucial oncogenic proteins and are involved in several essential intracellular processes. The RAS protein has an intrinsic metal binding site for Mg²⁺, which is important for the conformational stability of the active site. Recently, it was reported that a second metal ion binding site, located further from the active site in HRAS, binds Ca²⁺ with millimolar affinity.</span><span> As one of the most abundant metal ions in cells, Mn²⁺ is a potential candidate for the second metal ion binding site in RAS proteins. Here, we examined the interaction of Mn²⁺ with HRAS and KRAS using high resolution NMR spectroscopy. The NMR data showed that both the second metal ion binding site and the switch I and II regions bind Mn²⁺ in the RAS proteins. Furthermore, our paramagnetic NMR results disclosed the conformational differences in helix </span><span>a</span><span>3 and the following loop between HRAS and KRAS, accompanied by the association with metal ion binding. These results provide new insights into the interaction of RAS proteins and Mn²⁺ in the respective biological processes in cells.</span></p>