Molecular cloning and functional expression of a novel human gene encoding two 41-43 kDa skeletal muscle internal membrane proteins.

Systematic analysis of gene transcript repertoires prepared from libraries made with various specific human tissues permitted isolation of many partially sequenced cDNA clones. A few of these represented novel genes with limited or no similarity to known genes from humans or other species. The present study set out to isolate and sequence the full-length cDNA corresponding to one of these novel human transcripts, and identify the corresponding protein product at the subcellular level. Current sequence analyses have revealed that the protein contains a hydrophobic N-terminal segment and an internal leucine-zipper motif. Numerous sites of putative post-translational modifications, such as N-linked glycosylation, myristoylation and phosphorylation sites, were also identified. Using one monoclonal antibody raised against a recombinant fragment, two different 41-43 kDa proteins were detected in human skeletal muscle, heart and placenta homogenates at various ratios. Both immunodetected protein products of the novel human gene were distributed in the transverse tubules and/or near the junctional sarcoplasmic reticulum within skeletal muscle cells. Both proteins had physical properties believed to be attributable to integral membrane components. Finally, the GENX-3414 gene was chromosomally localized at position 4q24-q25.