Kinetic Analysis of Adenovirus Fiber Binding to Its Receptor Reveals an Avidity Mechanism for Trimeric Receptor-Ligand Interactions

Abstract

Most adenoviruses bind to the N-terminal immunoglobulin domain D1 of the coxsackievirus and adenovirus receptor via the head part of their fiber proteins. Three receptor molecules can bind per fiber head. We expressed the D1 domain and the adenovirus type 2 fiber head in bacteria and studied binding interactions by surface plasmon resonance measurements. When receptor domains bind adenovirus fiber independently of each other, the dissociation constant is 20 -25 nM. However, when adenovirus fiber binds to receptors immobilized on the sensor chip, a situation better mimicking adenovirus binding to receptors on the cell surface, the dissociation constant was around 1 nM. Kinetic analysis shows that this happens via an avidity mechanism; three identical interactions with high on and off rate constants lead to tight binding of one fiber head to three receptor molecules with a very low overall off rate. The avidity mechanism could be used by other viruses that have multimeric adhesion proteins to attach to target cells. It could also be more general to trimeric receptorligand interactions, including those involved in intracellular signaling.

Structural Basis for Variation in Adenovirus Affinity for the Cellular Coxsackievirus and Adenovirus Receptor

“…Mutational analysis of the CAR binding activities of Ad5 and Ad12 knobs is consistent with the Ad12 knob-CAR D1 x-ray structure, suggesting that the location of the CAR D1-binding sites on knob domains from different serotypes is conserved (24,30). The trimeric knob domain has three identical binding sites for CAR D1 that can be occupied simultaneously, as observed in the x-ray structure of the binary complex and in surface plasmon resonance experiments (24,31).…”

“…This extensive variation of contact residues implies that the mechanism of knob-CAR interaction could differ significantly among adenovirus serotypes. Individual contact residues at structurally analogous positions might differ considerably in their relative contributions to binding affinity, as suggested recently in a comparison of the interaction of recombinant knob domains from Ad5 and Ad9 with CAR D1 (31,32). One question arising from such studies is whether the relative positions of knob and CAR D1 in binary complexes changes significantly with the variation of contact residues in the knob component.…”

Bisphosphonate-mediated gene vector delivery from the metal surfaces of stents

“…Our Ad-release studies, carried out in an acellular system, demonstrated a somewhat higher dissociation rate for virus tethered via anti-knob antibody vs. D1-tethered Ad, confirming tighter binding with the immobilized receptor protein. Furthermore, it has been shown that the initial binding event of Ad to immobilized dimeric D1 has a much lower affinity (K d ϭ 20 nM) than an observed secondary binding event (K d ϭ 1 nM), thus suggesting that conformational changes of covalently attached D1 could actually facilitate more rapid release of Ad than would be otherwise expected (31). Thus, higher Ad binding with D1 tethering and facilitated release͞transduction in the presence of cells are not mutually exclusive.…”

“…Furthermore, based on elemental analysis, the estimated molecular mass of PAA-BP is Ϸ30 kDa, as calculated by using the sums of the weights of modified (245.1 Da) and nonmodified (57.1 Da) allylamine residues. 31 P NMR of pure PAA-BP documented a single peak at ␦ 16 ppm. In the 13 C NMR spectrum of nonmodified PAA⅐HCl (Fig.…”

Crystal Structure of Bacteriophage SPP1 Distal Tail Protein (gp19.1)

“…SPP1 (and the lactococcal phage c2 (46)) binds reversibly to saccharides in a first specific step and then interacts irreversibly with the membrane protein YueB (47,48). Affinity for saccharides is generally low (ϳmicromo-lar) and several RBPs are involved in binding to get strong interactions through avidity phenomena (7,8,9,14,(41)(42)(43)52). In contrast, binding to proteinaceous receptors is strong, as exemplified by the nanomolar affinity of coliphage T5 for its receptor FhuA (49,50).…”