Structural features of human Hsp70 proteins. Typical Hsp70 structures comprise two major domains: ATP-binding domain (ABD) and substrate-binding domain (SBD). The regions comprising the crystal structure of the ABD (1s3x , human HSPA1A, positions 1–382) and the NMR structure of the SBD (1ckr , rat HSPA8, corresponding to human HSPA8 and HSPA1A homologous positions 385–543) are shown as lines at the top of the figure. Domains conserved in human Hsp70 sequences within these regions are shown as aligned white boxes. Other domains conserved among groups of sequences are shown as aligned boxes of matching colors. Roman numerals to the left indicate the Hsp70 evolutionary groups. UBP, ubiquitin-binding peptide; TPR1, tetratrico peptide repeat 1; ER, endoplasmic reticulum. See text for other details.