Alam Steven L, Sun Ji, Payne Marielle, Welch Brett D, Blake B Kelly, Davis Darrell R, Meyer Hemmo H, Emr Scott D, Sundquist Wesley I
Department of Biochemistry, University of Utah, Salt Lake City, UT, USA.
EMBO J. 2004 Apr 7;23(7):1411-21. doi: 10.1038/sj.emboj.7600114. Epub 2004 Mar 18.
Ubiquitin (Ub) functions in many different biological pathways, where it typically interacts with proteins that contain modular Ub recognition domains. One such recognition domain is the Npl4 zinc finger (NZF), a compact zinc-binding module found in many proteins that function in Ub-dependent processes. We now report the solution structure of the NZF domain from Npl4 in complex with Ub. The structure reveals that three key NZF residues (13TF14/M25) surrounding the zinc coordination site bind the hydrophobic 'Ile44' surface of Ub. Mutations in the 13TF14/M25 motif inhibit Ub binding, and naturally occurring NZF domains that lack the motif do not bind Ub. However, substitution of the 13TF14/M25 motif into the nonbinding NZF domain from RanBP2 creates Ub-binding activity, demonstrating the versatility of the NZF scaffold. Finally, NZF mutations that inhibit Ub binding by the NZF domain of Vps36/ESCRT-II also inhibit sorting of ubiquitylated proteins into the yeast vacuole. Thus, the NZF is a versatile protein recognition domain that is used to bind ubiquitylated proteins during vacuolar protein sorting, and probably many other biological processes.
泛素（Ub）在许多不同的生物途径中发挥作用，在这些途径中它通常与含有模块化Ub识别结构域的蛋白质相互作用。其中一个这样的识别结构域是Npl4锌指（NZF），它是一种紧凑的锌结合模块，存在于许多参与Ub依赖过程的蛋白质中。我们现在报告了与Ub结合的Npl4的NZF结构域的溶液结构。该结构显示，围绕锌配位位点的三个关键NZF残基（13TF14/M25）与Ub的疏水“Ile44”表面结合。13TF14/M25基序中的突变会抑制Ub结合，而缺乏该基序的天然NZF结构域则不与Ub结合。然而，将13TF14/M25基序替换到RanBP2的非结合NZF结构域中会产生Ub结合活性，这证明了NZF支架的多功能性。最后，抑制Vps36/ESCRT-II的NZF结构域与Ub结合的NZF突变也会抑制泛素化蛋白进入酵母液泡的分选过程。因此，NZF是一种多功能的蛋白质识别结构域，在液泡蛋白分选过程中用于结合泛素化蛋白，可能还参与许多其他生物过程。
