Key component of the ribosome quality control system (RQC), a ribosome-associated complex that mediates the extraction of incompletely synthesized nascent chains from stalled ribosomes and their subsequent degradation. RqcH recruits Ala-charged tRNA, and with RqcP directs the elongation of stalled nascent chains on 50S ribosomal subunits, leading to non-templated C-terminal alanine extensions (Ala tail). The Ala tail promotes nascent chain degradation. RqcP is associated with the translocation-like movement of the peptidyl-tRNA from the A-site into the P-site