Expression and chromosomal localization of the human alpha 4/IGBP1 gene, the structure of which is closely related to the yeast TAP42 protein of the rapamycin-sensitive signal transduction pathway.

To study the function of the B cell signal transduction molecule alpha 4 (IGBP1), we isolated a human alpha 4 (IGBP1) gene that has sequence similarity to the yeast protein (TAP42) involved in the rapamycin-sensitive signal transduction pathway. The human alpha 4 has sequence identities with murine alpha 4 of 83.4% nucleotide and 82.9% amino acid sequence, and a stretch of consensus motifs in the carboxyl terminal is conserved among the related genes of human, mouse, yeast, and rice. The gene is expressed as a 1.4-kb mRNA in the spleen, lymph node, thymus, appendix, peripheral blood leukocytes, bone marrow, fetal liver, heart, brain, placenta, skeletal muscle, kidney, and pancreas. The anti-human alpha 4 antibody detected a 45-kDa protein in human lymphoid cell lines. Moreover, human alpha 4 (IGBP1) gene is located at q13.1-q13.3 on chromosome X.