Structure

The protein in its longest form has 8 exons. There is another possible isoform, but experimental confirmation is lacking – possibly due to it being produced at low levels because of an immature stop codon.^[7] Bioinformatic analysis suggests that the protein does not have transmembrane structure and is composed of both alpha helixes and beta sheets. There have been conflicting numbers for SPATS1 isoelectric points. Several sources have said 6.68, while two others suggested that it is higher, 7.04 and 7.47.^[8][9][10]

Subcellular location

Studies have suggested that most of the expression is found in the cytoplasm of the cell, but there is also evidence of expression in the nucleus.^[11] Expression in the nucleus may be supported by the fact that the rat homolog of the SPATS1 gene was experimentally found to have a probable bipartite nuclear localization signal.^[12] In addition, bioinformatic tools have identified a bipartite nuclear localization signal with high probability in the human protein at amino acids 174 - 191.^[13]

Post-translational modifications

Bioinformatic analysis suggests that it undergoes several post-translational modifications. The more plausible ones propose a GPI – modification site at amino acid 280, N-glycosylation sites at amino acids 49 and 229, and a phosphorylation site at amino acid 113. There are 85 predicted sites of phosphorylation, 23 having an 80% or higher likelihood.^[14] Only the one located at amino acid 113 has been experimentally confirmed.^[5] There is also a high probability of a SASRP1 motif that spans amino acids 51 - 288.^[15]

Protein interactions

Possible interacting proteins are listed in the table below. Note that these proteins have not been experimentally confirmed to interact with SPATS1. Instead, their interaction potential was determined by looking

The image above is a predicted secondary structure of the SPATS1 protein. This prediction was generated using I-TASSER.

at concurrence patterns and textmining.^[16]

The image above is a schematic drawing of the SPATS1 protein. Green represents sites of N-Glycosylation, red represents experimentally confirmed sites of phosphorylation, yellow represents GPI - modification sites, the purple bar represents the Bipartite nuclear localization signal, and pink represents the SASRP1 motif.

Regulation

The expression of this protein has been found to greatly decline in adulthood, compared to expression levels measured in fetuses.^[11] Studies have shown some fluctuation during the gestation period, but overall remaining relatively high. There has also been evidence of high expression levels up until day 28 postpartum.^[17]

Location

Expression of this protein has been found in peritubular myoid cells, gonocytes, pachytene spermatocytes, spermatogonia, myoid cells, and Sertoli cells.^[11]

The image on the left represents a heat map of the expression levels of the SPATS1 protein in the pituitary gland. The picture on the right shows a scale for the color and shown and the coordinating expression level. These images were generated using Brain Allen.

Mouse brains have shown expression in various areas of the brain including the pituitary gland, the prefrontal cortex, the frontal lobe, the cerebellum, and the parietal lobe.^[18] Highest expression levels have been found in the testes, the next highest levels being found in the trachea. A protein abundance histogram, which compares the abundance of a desired protein to other proteins, shows that SPATS1 is on the lower level of expression.^[5]