Characterization and Evolutionary Analysis of Non-Canonical Heat Shock Protein 70 Family Members in Metazoan.

To broaden the scope of research on the characteristics and evolutionary relationships within the heat shock protein 70 (Hsp70) family, encompassing its non-canonical members, amino acid sequences of Hsp70-12, Hsp70-13, and Hsp70-14, alongside those of traditional Hsp70, were collected and analyzed. The findings indicate that, during the evolution of metazoans, the various Hsp70 groups diverged from one another. Specifically, Hsp70-12 emerges as the least conserved member, as evidenced by structural alignment data and the Ka/Ks ratio. It not only represents the most distantly related group to traditional Hsp70 but also stands out as the sole alkaline group within the family. In contrast, Hsp70-13 exhibits a close evolutionary relationship with traditional Hsp70, albeit with the notable loss of its C-terminal domain. Hsp70-14 occupies an intermediate position between Hsp70-12 and Hsp70-13. Phylogenetic analysis suggests that these groups diverged prior to the advent of invertebrates. Furthermore, five conserved motifs within the ATP-binding domain of Hsp70, which serve as distinguishing features for Hsp70 groups, were identified. The diverse characters of the non-canonical Hsp70s are probably related to their special cellular location and tissue specificity. Together, the results of this research will help identify and categorize Hsp70s. Further research that aims at identifying additional non-canonical Hsp70 members and elucidating the distinct characteristics and functions of these molecular chaperones will enhance our comprehension of the origin and evolutionary trajectory of the Hsp70 family.