Forms spikes that protrude from each vertex of the icosahedral capsid. Interacts with host coxsackievirus and adenovirus receptor CXADR located at the cell tight junctions to provide virion initial attachment to target cell. The fiber protein binds to CXADR with a higher affinity than CXADR binds to itself, thereby blocking the cell-cell adhesion function of CXADR dimers and leading to local disruption of the tight junction. Fiber protein present on neo-synthesized particles may thus disrupt the junctional integrity in order to facilitate further neighboring cells infection. Fiber proteins are shed during virus entry, when virus is still at the cell surface. Fiber shedding is dependent on viral CXADR drifting motion and subsequent binding to immobile integrins. Heparan sulfate might also play a role in virus binding. Homotrimer; arranged in a triple beta-spiral. Interacts with host receptor CXADR. Interacts (via N-terminal tail region) with pentons (Probable). Anchored to the pentons, protrudes from the virion surface. Present in 36 copies per virion. Expressed in the late phase of the viral replicative cycle. The tail region anchors the fiber to penton base capsomers, whereas the shaft, built from several repeated motifs, allows the knob to protrude from the virion. O-glycosylated; glycans contain N-acetylglucosamine and may play a role in fiber assembly and stabilization. All late proteins expressed from the major late promoter are produced by alternative splicing and alternative polyadenylation of the same gene giving rise to non-overlapping ORFs. A leader sequence is present in the N-terminus of all these mRNAs and is recognized by the viral shutoff protein to provide expression although conventional translation via ribosome scanning from the cap has been shut off in the host cell. Belongs to the adenoviridae fiber family.