Dimeric molecular motor myosin V transports cargoes towards the barbed end of actin filaments in cells, coordinating ATPase cycles in its two head domains to ensure the efficient unidirectional motility. Directional loads modulate the kinetics of nucleotide binding to myosin V, suggesting that the head-head communication may be achieved via intramolecular load, generated when both heads are bound to actin. Here, using point mutations in the converter domain, we directly tested the effect of the intramolecular load on the processive stepping of myosin V. The converter is a compact structure, which transmits tiny conformational changes, induced at the nucleotide-binding site in the process of ATP hydrolysis, to the lever arm. To disturb the transmission mechanism, we replaced with alanines, one at a time, two phenylalanine residues that form a hydrophobic cluster with the C-terminus of the relay helix. We found that the F749A mutation, which is inferred to reduce intramolecular load but does not affect the nucleotide binding or actin affinity, significantly increases the proportion of backward steps, providing strong experimental evidence that the efficient unidirectional processive stepping of myosin V and, possibly, other dimeric processive motors, is ensured by the head-head communication based on the intramolecular load, which coordinates ATPase cycles in two motor domains.