Crystal structure of enteric adenovirus serotype 41 short fiber head

Human enteric adenoviruses of species F contain two fibers in the same virion, a long fiber which binds to coxsackievirus and adenovirus receptor (CAR) and a short fiber of unknown function. We have determined the high-resolution crystal structure of the short fiber head of human adenovirus serotype 41 (Ad41). The short fiber head has the characteristic fold of other known fiber heads but has three unusual features. First, it has much shorter loops between the beta-strands. Second, one of the usually well-ordered beta-strands on the distal face of the fiber head is highly disordered and this same region is sensitive to digestion with pepsin, an enzyme occurring naturally in the intestinal tract, the physiological environment of Ad41. Third, the AB loop has a deletion giving it a distinct conformation incompatible with CAR binding.