Ab initio modeling of the herpesvirus VP26 core domain assessed by CryoEM density.
Efforts in structural biology have targeted the systematic determination of all protein structures through experimental determination or modeling. In recent years, 3-D electron cryomicroscopy (cryoEM) has assumed an increasingly important role in determining the structures of these large macromolecular assemblies to intermediate resolutions (6-10 A). While these structures provide a snapshot of the assembly and its components in well-defined functional states, the resolution limits the ability to build accurate structural models. In contrast, sequence-based modeling techniques are capable of producing relatively robust structural models for isolated proteins or domains. In this work, we developed and applied a hybrid modeling approach, utilizing cryoEM density and ab initio modeling to produce a structural model for the core domain of a herpesvirus structural protein, VP26. Specifically, this method, first tested on simulated data, utilizes the cryoEM density map as a geometrical constraint in identifying the most native-like models from a gallery of models generated by ab initio modeling. The resulting model for the core domain of VP26, based on the 8.5-A resolution herpes simplex virus type 1 (HSV-1) capsid cryoEM structure and mutational data, exhibited a novel fold. Additionally, the core domain of VP26 appeared to have a complementary interface to the known upper-domain structure of VP5, its cognate binding partner. While this new model provides for a better understanding of the assembly and interactions of VP26 in HSV-1, the approach itself may have broader applications in modeling the components of large macromolecular assemblies.
Baker
Matthew L
ML
National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America.
Jiang
Wen
W
Wedemeyer
William J
WJ
Rixon
Frazer J
FJ
Baker
David
D
Chiu
Wah
W
D015502:Absorptiometry, Photon / Q000379:methods*; D000595:Amino Acid Sequence; D036022:Capsid Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D003198:Computer Simulation; D020285:Cryoelectron Microscopy / Q000379:methods*; D003461:Crystallography / Q000379:methods; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
D036022:Capsid Proteins; C077409:capsid protein VP26, herpes simplex virus type 1