Dataset Information

Intermediate-resolution crystal structure of the human adenovirus B serotype 3 fibre knob in complex with the EC2-EC3 fragment of desmoglein 2.

ABSTRACT: The cryo-electron microscopy (cryo-EM) structure of the complex between the trimeric human adenovirus B serotype 3 fibre knob and human desmoglein 2 fragments containing cadherin domains EC2 and EC3 has been published, showing 3:1 and 3:2 complexes. Here, the crystal structure determined at 4.5?Å resolution is presented with one EC2-EC3 desmoglein fragment bound per fibre knob monomer in the asymmetric unit, leading to an apparent 3:3 stoichiometry. However, in concentrated solution the 3:2 complex is predominant, as shown by small-angle X-ray scattering (SAXS), while cryo-EM at lower concentrations showed a majority of the 3:1 complex. Substitution of the calcium ions bound to the desmoglein domains by terbium ions allowed confirmation of the X-ray model using their anomalous scattering and shows that at least one binding site per cluster of calcium ions is intact and exchangeable and, combined with SAXS data, that the cadherin domains are folded even in the distal part that is invisible in the cryo-EM reconstruction.

SUBMITTER: Vassal-Stermann E

PROVIDER: S-EPMC6891581 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Intermediate-resolution crystal structure of the human adenovirus B serotype 3 fibre knob in complex with the EC2-EC3 fragment of desmoglein 2.

Vassal-Stermann Emilie E Hutin Stephanie S Fender Pascal P Burmeister Wim P WP

Acta crystallographica. Section F, Structural biology communications 20191127 Pt 12

The cryo-electron microscopy (cryo-EM) structure of the complex between the trimeric human adenovirus B serotype 3 fibre knob and human desmoglein 2 fragments containing cadherin domains EC2 and EC3 has been published, showing 3:1 and 3:2 complexes. Here, the crystal structure determined at 4.5 Å resolution is presented with one EC2-EC3 desmoglein fragment bound per fibre knob monomer in the asymmetric unit, leading to an apparent 3:3 stoichiometry. However, in concentrated solution the 3:2 comp ...[more]

PMID: 31797817

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Project description:Most adenoviruses recognize their host cells via an interaction of their fibre head domains with a primary receptor. The structural framework of adenovirus fibre heads is conserved between the different adenovirus genera for which crystal structures have been determined (Mastadenovirus, Aviadenovirus, Atadenovirus and Siadenovirus), but genus-specific differences have also been observed. The only known siadenovirus fibre head structure, that of turkey adenovirus 3 (TAdV-3), revealed a twisted beta-sandwich resembling the reovirus fibre head architecture more than that of other adenovirus fibre heads, plus a unique beta-hairpin embracing a neighbouring monomer. The TAdV-3 fibre head was shown to bind sialyllactose.Raptor adenovirus 1 (RAdV-1) fibre head was expressed, crystallized and its structure was solved and refined at 1.5 Å resolution. The structure could be solved by molecular replacement using the TAdV-3 fibre head structure as a search model, despite them sharing a sequence identity of only 19 %. Versions of both the RAdV-1 and TAdV-3 fibre heads with their beta-hairpin arm deleted were prepared and their stabilities were compared with the non-mutated proteins by a thermal unfolding assay.The structure of the RAdV-1 fibre head contains the same twisted ABCJ-GHID beta-sandwich and beta-hairpin arm as the TAdV-3 fibre head. However, while the predicted electro-potential surface charge of the TAdV-3 fibre head is mainly positive, the RAdV-1 fibre head shows positively and negatively charged patches and does not appear to bind sialyllactose. Deletion of the beta-hairpin arm does not affect the structure of the raptor adenovirus 1 fibre head and only affects the stability of the RAdV-1 and TAdV-3 fibre heads slightly.The high-resolution structure of RAdV-1 fibre head is the second known structure of a siadenovirus fibre head domain. The structure shows that the siadenovirus fibre head structure is conserved, but differences in the predicted surface charge suggest that RAdV-1 uses a different natural receptor for cell attachment than TAdV-3. Deletion of the beta-hairpin arm shows little impact on the structure and stability of the siadenovirus fibre heads.

Project description:BackgroundIn adenoviruses, primary host cell recognition is generally performed by the head domains of their homo-trimeric fibre proteins. This first interaction is reversible. A secondary, irreversible interaction subsequently takes place via other adenovirus capsid proteins and leads to a productive infection. Although many fibre head structures are known for human mastadenoviruses, not many animal adenovirus fibre head structures have been determined, especially not from those belonging to adenovirus genera other than Mastadenovirus.MethodsWe constructed an expression vector for the fibre head domain from a ruminant atadenovirus, bovine adenovirus 4 (BAdV-4), consisting of amino acids 414-535, expressed the protein in Escherichia coli, purified it by metal affinity and cation exchange chromatography and crystallized it. The structure was solved using single isomorphous replacement plus anomalous dispersion of a mercury derivative and refined against native data that extended to 1.2 Å resolution.ResultsLike in other adenoviruses, the BAdV-4 fibre head monomer contains a beta-sandwich consisting of ABCJ and GHID sheets. The topology is identical to the fibre head of the other studied atadenovirus, snake adenovirus 1 (SnAdV-1), including the alpha-helix in the DG-loop, despite of them having a sequence identity of only 15 %. There are also differences which may have implications for ligand binding. Beta-strands G and H are longer and differences in several surface-loops and surface charge are observed.ConclusionsChimeric adenovirus fibres have been used to retarget adenovirus-based anti-cancer and gene therapy vectors. Ovine adenovirus 7 (OAdV-7), another ruminant atadenovirus, is intensively tested as a basis for such a vector. Here, we present the high-resolution atomic structure of the BAdV-4 fibre head domain, the second atadenovirus fibre head structure known and the first of an atadenovirus that infects a mammalian host. Future research should focus on the receptor-binding properties of these fibre head domains.

Dataset Information

Intermediate-resolution crystal structure of the human adenovirus B serotype 3 fibre knob in complex with the EC2-EC3 fragment of desmoglein 2.

Publications

Intermediate-resolution crystal structure of the human adenovirus B serotype 3 fibre knob in complex with the EC2-EC3 fragment of desmoglein 2.

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