Structural component of the proximal-half of the long-tail fiber. The long-tail fibers of T4 are about 1600 Angstroms long with a kink in the middle that divides the fiber into proximal and distal halves. The long-tail fibers are trimeric, with a stoichiometry of gp34/gp37/gp36/gp35 of 3:3:3:1. Belongs to the tevenvirinae long-tail fiber proximal subunit protein family.