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Sigma-1 non-opioid intracellular receptor SGMR-1, OPRS1, SRBP, AAG8) of 223 aas and 2 or 3 TMSs.  It influences the activities of various channels and carriers including L-type Ca2+ channels (Tchedre et al. 2008) and the dopamine transporter, DAT (2.A.22.1.3; Hong et al. 2017). Sigma-1 receptors play a negative modulation role on N-type Ca2+ channels involving chaperone-mediated direct interactions (Zhang et al. 2017). The sigma-1 receptor is a theraputic target in retinal disease (Smith et al. 2018). The sigma1R E102Q mutant exhibits an anomalous response to cytosolic calcium levels, altered affinity for target proteins, and a loss of response to regulatory ligands, and these modifications may contribute to the onset of juvenile ALS (Rodríguez-Muñoz et al. 2020). Sigmar1 localizes to mitochondrial membranes and is indispensable for maintaining mitochondrial respiratory homeostasis in cardiomyocytes (Abdullah et al. 2021). It helps to locate endoplasmic reticulum calcium channels, regulates calcium homeostasis, and acts as a molecular chaperone to control cell fate and participate in signal transduction. It plays a role in protecting neurons through a variety of signaling pathways and participates in the regulation of cognition and motor behavior closely related to neurodegenerative diseases. Sig-1R is a target for alleviating Alzheimer's disease and other neurodegenerative diseases (Wu et al. 2021).

Metazoa, Chordata
Sigma-1 receptor of Homo sapiens

The ERG2 and sigma1 receptor-like protein of 194 aas and 2 TMSs

Fungi, Basidiomycota
Sigma-1 recpeptor of Trichosporon oleaginosus

C-8 sterol isomerase of 217 aas and 3 TMSs.

Fungi, Ascomycota
isomerase of Candida dubliniensis

Uncharacterized protein of 374 aas and 2 - 3 TMSs.

Viridiplantae, Streptophyta
UP of Vitis vinifera (Grape)

Uncharacterized protein of 228 aas and 3 mildly hydrophobic peaks.

Metazoa, Nematoda
UP of Caenorhabditis elegans

C8 sterol isomerase of 191 aas and 1 - 3 putative TMSs.

Isomerase of Mycobacterium gilvum