The AAA-type ATPase Cdc48 (named p97/VCP in mammals) is a molecular machine in 
all eukaryotic cells that transforms ATP hydrolysis into mechanic power to 
unfold and pull proteins against physical forces, which make up a protein's 
structure and hold it in place. From the many cellular processes, Cdc48 is 
involved in, its function in endoplasmic reticulum associated protein 
degradation (ERAD) is understood best. This quality control process for proteins 
of the secretory pathway scans protein folding and discovers misfolded proteins 
in the endoplasmic reticulum (ER), the organelle, destined for folding of these 
proteins and their further delivery to their site of action. Misfolded lumenal 
and membrane proteins of the ER are detected by chaperones and lectins and 
retro-translocated out of the ER for degradation. Here the Cdc48 machinery, 
recruited to the ER membrane, takes over. After polyubiquitylation of the 
protein substrate, Cdc48 together with its dimeric co-factor complex Ufd1-Npl4 
pulls the misfolded protein out and away from the ER membrane and delivers it to 
down-stream components for degradation by a cytosolic proteinase machine, the 
proteasome. The known details of the Cdc48-Ufd1-Npl4 motor complex triggered 
process are subject of this review article.