ABSTRACT
Human species C adenovirus serotype 5 (Ad5) is the most common viral vector used in clinical studies worldwide. Ad5 vectors infect liver cells in vivo with high efficiency via a poorly defined mechanism, which involves virus binding to vitamin K-dependent blood coagulation factors. Here, we report that the major Ad5 capsid protein, hexon, binds human coagulation factor X (FX) with an affinity of 229 pM. This affinity is 40-fold stronger than the reported affinity of Ad5 fiber for the cellular receptor coxsackievirus and adenovirus receptor, CAR. Cryoelectron microscopy and single-particle image reconstruction revealed that the FX attachment site is localized to the central depression at the top of the hexon trimer. Hexon-mutated virus bearing a large insertion in hexon showed markedly reduced FX binding in vitro and failed to deliver a transgene to hepatocytes in vivo. This study describes the mechanism of FX binding to Ad5 and demonstrates the critical role of hexon for virus infection of hepatocytes in vivo.
Subject(s)
Adenoviruses, Human/chemistry , Capsid Proteins/metabolism , Factor X/metabolism , Hepatocytes/virology , Virus Attachment , Adenovirus Infections, Human , Adenoviruses, Human/pathogenicity , Binding Sites , Capsid Proteins/physiology , Cells, Cultured , Cryoelectron Microscopy , Humans , Protein BindingABSTRACT
The crystal structure of Pfal009167AAA, a putative ribulose 5-phosphate 3-epimerase (PfalRPE) from Plasmodium falciparum, has been determined to 2 A resolution. RPE represents an exciting potential drug target for developing antimalarials because it is involved in the shikimate and the pentose phosphate pathways. The structure is a classic TIM-barrel fold. A coordinated Zn ion and a bound sulfate ion in the active site of the enzyme allow for a greater understanding of the mechanism of action of this enzyme. This structure is solved in the framework of the Structural Genomics of Pathogenic Protozoa (SGPP) consortium.