Su Minfei, Li Yue, Wyborny Shane, Neau David, Chakravarthy Srinivas, Levine Beth, Colbert Christopher L, Sinha Sangita C
Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota, 58108-6050.
Department of Chemistry and Chemical Biology, Cornell University, Northeastern Collaborative Access Team, Argonne National Laboratory, Argonne, Illinois, 60439.
Protein Sci. 2017 May;26(5):972-984. doi: 10.1002/pro.3140. Epub 2017 Mar 12.
ATG14 binding to BECN/Beclin homologs is essential for autophagy, a critical catabolic homeostasis pathway. Here, we show that the α-helical, coiled-coil domain (CCD) of BECN2, a recently identified mammalian BECN1 paralog, forms an antiparallel, curved homodimer with seven pairs of nonideal packing interactions, while the BECN2 CCD and ATG14 CCD form a parallel, curved heterodimer stabilized by multiple, conserved polar interactions. Compared to BECN1, the BECN2 CCD forms a weaker homodimer, but binds more tightly to the ATG14 CCD. Mutation of nonideal BECN2 interface residues to more ideal pairs improves homodimer self-association and thermal stability. Unlike BECN1, all BECN2 CCD mutants bind ATG14, although more weakly than wild type. Thus, polar BECN2 CCD interface residues result in a metastable homodimer, facilitating dissociation, but enable better interactions with polar ATG14 residues stabilizing the BECN2:ATG14 heterodimer. These structure-based mechanistic differences in BECN1 and BECN2 homodimerization and heterodimerization likely dictate competitive ATG14 recruitment.
ATG14与BECN/Beclin同源物的结合对于自噬这一关键的分解代谢稳态途径至关重要。在此，我们表明，最近鉴定出的哺乳动物BECN1旁系同源物BECN2的α螺旋卷曲螺旋结构域（CCD）形成了一种具有七对非理想堆积相互作用的反平行弯曲同二聚体，而BECN2 CCD和ATG14 CCD形成了一种由多个保守极性相互作用稳定的平行弯曲异二聚体。与BECN1相比BECN2 CCD形成的同二聚体较弱，但与ATG14 CCD的结合更紧密。将非理想的BECN2界面残基突变为更理想的配对可改善同二聚体的自缔合和热稳定性。与BECN1不同，所有BECN2 CCD突变体都能结合ATG14，尽管其结合能力比野生型弱。因此，极性的BECN2 CCD界面残基导致形成一种亚稳态同二聚体，便于解离，但能与极性的ATG14残基形成更好的相互作用，从而稳定BECN2:ATG14异二聚体。BECN1和BECN2在同二聚化和异二聚化方面基于结构的机制差异可能决定了ATG14的竞争性募集。
