| Type: | Domain | Name: | DNA polymerase III/inhibitor IA3, alpha-helix domain |
| Description: | This entry represents a single alpha-helix domain involved in coiled-coils or other helix-helix interfaces. It is found in polC-type DNA polymerase III, and in the yeast proteinase inhibitor IA3 [].DNA polymerase III PolC-type is required for replicative DNA synthesis and also exhibits 3' to 5' exonuclease activity.The IA3 polypeptide of Saccharomyces cerevisiae (also known as Pai3) is an 8kDa inhibitor of the vacuolar aspartic proteinase (proteinase A or saccharopepsin, MEROPS peptidase family A1). It belongs to MEROPS inhibitor family I34, clan JA. No other aspartic proteinase has been found to be inhibited by IA3, and at least 15 aspartic proteinases related to YprA cleave IA3 as a substrate. Ligand- free IA3 has little intrinsic secondary structure, however, upon contact with proteinase A, residues 2-32 of the inhibitor become ordered and adopt a near perfect alpha-helical conformation occupying the active site cleft of the enzyme. This potent, specific interaction is directed primarily by hydrophobic interactions made by three key features in the inhibitory sequence []. | Short Name: | DNA_polIII_IA3_alpha-helix |
