This gene is expressed in a variety of human tissues, the highest being in the ovary and testis. It is expressed at higher levels in malignant mesotheliomas than in normal mesothelial cells.
General function
Channel/transport protein
Comment
From a fetal mouse mandibular condyle cDNA library, Hong et al. (1996) isolated a novel cDNA coding for a highly hydrophobic protein that the authors called B5. The full-length mouse B5 cDNA was 3,095 nucleotides long and contained a potential open reading frame coding for a protein of 705 amino acids with a calculated molecular mass of 80.5 kD. The B5 mRNA was differentially polyadenylated, with the most abundant transcript
having a length of 2.7 kb. Hong et al. (1996) isolated the human homolog of B5 from a cDNA testis library. The amino acid sequence of the human B5 was 98.5% identical to that of the mouse protein. A striking feature of the B5 protein was the presence of numerous (10 to 14) potential transmembrane domains, characteristic of an integral membrane protein. Similarity searches in public databases revealed that B5 is 58% similar to the T12A2.2 gene of C. elegans and 60% similar to the STT3 gene of S. cerevisiae. A human EST related to human B5 and identical to the STT3 gene
indicated to Hong et al. (1996) that B5 belongs to a larger gene family coding for novel putative transmembrane proteins. They observed that this
family exhibits a remarkable degree of conservation across species.
Cellular localization
Plasma membrane
Comment
Ovarian function
Comment
Expression regulated by
Comment
Lissy et al. (1996) used differential display PCR to identify genes expressed at higher levels in malignant mesotheliomas than in normal mesothelial cells. They isolated and cloned from a human fetal brain library a full-length ITM1 cDNA, which they termed TMC. The predicted 705-amino acid protein has 13 putative transmembrane domains. Northern blot analysis revealed that the gene is expressed in a variety of human tissues, with highest
expression in ovary and testis. Northern blot and RT-PCR analysis showed no differences in the level of expression among normal and malignant mesothelial cell lines tested.