Two-hybrid system. (a) Oligomeric character of the baits used in the two-hybrid system. Yeast extracts expressing head domains of the Ad41 short and long fibers in fusion with binding domains (BD-HSF41 and BD-HLF41) were analyzed on PAGE under denatured and semidenatured (no boiling) conditions. The baits were revealed with anti Ad2-fiber protein. T—trimer, M—monomer. (b) Yeast mating test. The plasmids of the positive clones were isolated and used for transformation of the Y187a yeast strain. The baits: binding domain of GAL4 fused with the head domain of Ad41 short (HSF41) or long (HLF41) fibers or with the head domain of respiratory Ad2 strain fiber (H2) and the controls (negative—pAS and LAM, a positive—VA3), all in the Y190a strain, were mated with the positive clones in Y187a.