1.R.1.1.2
ATPase family AAA domain-containing protein 1 isoform 1, Msp1 or ATAD1, is a P5A-ATPase of 361 aas and 1 N-terminal TMS. It is a conserved eukaryotic AAA+ ATPase localized to the outer mitochondrial membrane, where it may extract mislocalized tail-anchored proteins (McKenna et al. 2020). Msp1's ATPase activity depends on its hexameric state. Castanzo et al. 2020 showed that Msp1 is a robust bidirectional protein translocase that is able to unfold diverse substrates by processive threading through its central pore. This unfoldase activity is inhibited by Pex3, a membrane protein proposed to regulate Msp1 at the peroxisome surface (Castanzo et al. 2020). This P5A-ATPase belongs to a eukaryotic-specific subfamily of P-type ATPases with previously unknown substrate specificity (McKenna et al. 2020). It interacts directly with mitochondrial tail-anchored proteins (McKenna et al. 2020). Msp1 (ATAD1 in mammals, also referred to as Thorase), can be found in the outer mitochondrial membrane and in peroxysomes as well as the ER (Dederer and Lemberg 2021). Structures of Spf1 (TC# 3.A.3.10.3) and this dismutase  reveal how they remove mislocalized TA proteins from the ER and outer mitochondrial membranes, respectively (Sinning and McDowell 2022).