1.A.131. The Putative TRP-like Channel (P-TRPL-Ch) Family
The proteins that comprise this family have been extensively characterized (see references cited for the various (putative) channel proteins in the family), but they are very distantly related (if at all) to other members of the TRP-CC family (TC# 1.A.4). The 1.A.131 family was previously part of the TRP-CC family with TC # 1.A.4.9. Then the great destance between the members of the TRP-CC and P-TRPL-Ch families was revealed, so the P-TRPL-Ch family was assigned its own family number. These proteins are large (~740 aas) with most, but not all, having a large hydrophilic domain with from 0-4 scattered TMSs, followed by 3 TMSs (possibly with a helix-p-loop-helix structure, as the central putative TMS is always the smallest hydrophobicity peak of the three). These three peaks are followed by but separated from four similarly hydrophobic peaks that are likely to be TMSs. Thus, the basic constant region of these proteins is the 3 + 4 C-terminal TMS region. Most members of this family are derived from fungi. These channels may act as ion transporters, transferring Ca2+ from the cytosol into the Golgi apparatus and maintaining cellular calcium homeostasis. Therefore, TrpR appears to function as a Golgi membrane calcium ion channel that is involved in cell wall integration (Wang et al. 2021).