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A sialic acid binding site in a human picornavirus.

Zocher G, Mistry N, Frank M, Hähnlein-Schick I, Ekström JO, Arnberg N, Stehle T - PLoS Pathog. (2014)

Bottom Line: Biochemical studies verified the relevance of the binding site and demonstrated a preference of CVA24v for α2,6-linked glycans.This preference can be rationalized by molecular dynamics simulations that show that α2,6-linked glycans can establish more contacts with the viral capsid.Our results form an excellent platform for the design of antiviral compounds to prevent AHC.

View Article: PubMed Central - PubMed

Affiliation: Interfaculty Institute of Biochemistry, University Tübingen, Tübingen, Germany.

ABSTRACT
The picornaviruses coxsackievirus A24 variant (CVA24v) and enterovirus 70 (EV70) cause continued outbreaks and pandemics of acute hemorrhagic conjunctivitis (AHC), a highly contagious eye disease against which neither vaccines nor antiviral drugs are currently available. Moreover, these viruses can cause symptoms in the cornea, upper respiratory tract, and neurological impairments such as acute flaccid paralysis. EV70 and CVA24v are both known to use 5-N-acetylneuraminic acid (Neu5Ac) for cell attachment, thus providing a putative link between the glycan receptor specificity and cell tropism and disease. We report the structures of an intact human picornavirus in complex with a range of glycans terminating in Neu5Ac. We determined the structure of the CVA24v to 1.40 Å resolution, screened different glycans bearing Neu5Ac for CVA24v binding, and structurally characterized interactions with candidate glycan receptors. Biochemical studies verified the relevance of the binding site and demonstrated a preference of CVA24v for α2,6-linked glycans. This preference can be rationalized by molecular dynamics simulations that show that α2,6-linked glycans can establish more contacts with the viral capsid. Our results form an excellent platform for the design of antiviral compounds to prevent AHC.

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Related in: MedlinePlus

CVA24v in complex with its glycan receptor.The capsid structure of CVA24v with the capsid proteins VP1 (light blue), VP2 (green), VP3 (red) is shown in a surface representation. VP4 is located inside the capsid not visible in this figure. The Neu5Ac entity (black) is located at a positively charged, solvent exposed region of VP1. The atoms of one pentameric section (left) are colored according to the electrostatic potential using a color scale from red to blue. The adjacent pentameric section (right) was colored according to the distance from the center of the capsid, ranging from blue (122 Å) to red (162 Å).
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ppat-1004401-g001: CVA24v in complex with its glycan receptor.The capsid structure of CVA24v with the capsid proteins VP1 (light blue), VP2 (green), VP3 (red) is shown in a surface representation. VP4 is located inside the capsid not visible in this figure. The Neu5Ac entity (black) is located at a positively charged, solvent exposed region of VP1. The atoms of one pentameric section (left) are colored according to the electrostatic potential using a color scale from red to blue. The adjacent pentameric section (right) was colored according to the distance from the center of the capsid, ranging from blue (122 Å) to red (162 Å).

Mentions: To establish a structural basis for the recognition of sialic acid by CVA24v, we first determined the structure of intact CVA24v, an isolate of the Malaysia outbreak occurring during the 2002–2004 AHC pandemic [5], at 1.40 Å resolution (Table 1, Figure S1). As is typical for picornaviruses, the four capsid proteins (VP1-4) assemble into an icosahedral pseudo T3-capsid [12], [20], [21] (Figure 1). VP1 is close to a fivefold axis of the capsid; VP2, close to a twofold; and VP3, close to a threefold. VP4 lies inside the capsid and carries a myristyl group at its N-terminus. Picornaviruses have so-called non-polar pocket factors that modulate the interactions to receptors of the immunoglobulin superfamily, e.g ICAM-1 and DAF since they bind in regions that lie beneath the receptor binding site of the picornavirus capsid (so-called “canyon”) [22]. An unbiased (Fo-Fc)-omit map clearly reveals the presence of a branched, elongated pocket factor in CVA24v (Figure S2). However, the identity of this molecule remains unclear, perhaps due to multiple conformations or an inhomogeneous mixture of pocket factors present in the virion. A structural comparison [23] of ten different homologous picornavirus capsids (Figure S3, Tables S1 and S2) shows that CVA24v differs primarily at the N-terminal and C-terminal regions and at the solvent-exposed loops of the “jelly-roll” fold proteins VP1, VP2, and VP3. Compared to the structural homologues the most substantial structural differences are observed in the BC- and DE-loops of the CVA24v capsid.


A sialic acid binding site in a human picornavirus.

Zocher G, Mistry N, Frank M, Hähnlein-Schick I, Ekström JO, Arnberg N, Stehle T - PLoS Pathog. (2014)

CVA24v in complex with its glycan receptor.The capsid structure of CVA24v with the capsid proteins VP1 (light blue), VP2 (green), VP3 (red) is shown in a surface representation. VP4 is located inside the capsid not visible in this figure. The Neu5Ac entity (black) is located at a positively charged, solvent exposed region of VP1. The atoms of one pentameric section (left) are colored according to the electrostatic potential using a color scale from red to blue. The adjacent pentameric section (right) was colored according to the distance from the center of the capsid, ranging from blue (122 Å) to red (162 Å).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4199766&req=5

ppat-1004401-g001: CVA24v in complex with its glycan receptor.The capsid structure of CVA24v with the capsid proteins VP1 (light blue), VP2 (green), VP3 (red) is shown in a surface representation. VP4 is located inside the capsid not visible in this figure. The Neu5Ac entity (black) is located at a positively charged, solvent exposed region of VP1. The atoms of one pentameric section (left) are colored according to the electrostatic potential using a color scale from red to blue. The adjacent pentameric section (right) was colored according to the distance from the center of the capsid, ranging from blue (122 Å) to red (162 Å).
Mentions: To establish a structural basis for the recognition of sialic acid by CVA24v, we first determined the structure of intact CVA24v, an isolate of the Malaysia outbreak occurring during the 2002–2004 AHC pandemic [5], at 1.40 Å resolution (Table 1, Figure S1). As is typical for picornaviruses, the four capsid proteins (VP1-4) assemble into an icosahedral pseudo T3-capsid [12], [20], [21] (Figure 1). VP1 is close to a fivefold axis of the capsid; VP2, close to a twofold; and VP3, close to a threefold. VP4 lies inside the capsid and carries a myristyl group at its N-terminus. Picornaviruses have so-called non-polar pocket factors that modulate the interactions to receptors of the immunoglobulin superfamily, e.g ICAM-1 and DAF since they bind in regions that lie beneath the receptor binding site of the picornavirus capsid (so-called “canyon”) [22]. An unbiased (Fo-Fc)-omit map clearly reveals the presence of a branched, elongated pocket factor in CVA24v (Figure S2). However, the identity of this molecule remains unclear, perhaps due to multiple conformations or an inhomogeneous mixture of pocket factors present in the virion. A structural comparison [23] of ten different homologous picornavirus capsids (Figure S3, Tables S1 and S2) shows that CVA24v differs primarily at the N-terminal and C-terminal regions and at the solvent-exposed loops of the “jelly-roll” fold proteins VP1, VP2, and VP3. Compared to the structural homologues the most substantial structural differences are observed in the BC- and DE-loops of the CVA24v capsid.

Bottom Line: Biochemical studies verified the relevance of the binding site and demonstrated a preference of CVA24v for α2,6-linked glycans.This preference can be rationalized by molecular dynamics simulations that show that α2,6-linked glycans can establish more contacts with the viral capsid.Our results form an excellent platform for the design of antiviral compounds to prevent AHC.

View Article: PubMed Central - PubMed

Affiliation: Interfaculty Institute of Biochemistry, University Tübingen, Tübingen, Germany.

ABSTRACT
The picornaviruses coxsackievirus A24 variant (CVA24v) and enterovirus 70 (EV70) cause continued outbreaks and pandemics of acute hemorrhagic conjunctivitis (AHC), a highly contagious eye disease against which neither vaccines nor antiviral drugs are currently available. Moreover, these viruses can cause symptoms in the cornea, upper respiratory tract, and neurological impairments such as acute flaccid paralysis. EV70 and CVA24v are both known to use 5-N-acetylneuraminic acid (Neu5Ac) for cell attachment, thus providing a putative link between the glycan receptor specificity and cell tropism and disease. We report the structures of an intact human picornavirus in complex with a range of glycans terminating in Neu5Ac. We determined the structure of the CVA24v to 1.40 Å resolution, screened different glycans bearing Neu5Ac for CVA24v binding, and structurally characterized interactions with candidate glycan receptors. Biochemical studies verified the relevance of the binding site and demonstrated a preference of CVA24v for α2,6-linked glycans. This preference can be rationalized by molecular dynamics simulations that show that α2,6-linked glycans can establish more contacts with the viral capsid. Our results form an excellent platform for the design of antiviral compounds to prevent AHC.

Show MeSH
Related in: MedlinePlus