Molecular cloning and characterization of a highly basic protein, IA-4, expressed in pancreatic islets and brain.
A substraction library was constructed from mouse insulinoma (betaTC-1) and glucagonoma (alphaTC-1) cell lines. Differential screening and sequencing revealed a novel cDNA clone, IA-4, which was expressed in the islets of Langerhans and the brain. IA-4 cDNA is 1,007 bp in length and predicts a protein of 187 amino acids with a molecular mass of 19,940 D. Examination of the amino acid sequence showed a high content of arginine (18.7%), proline (14.4%), alanine (16.0%), leucine (13.4%) and glycine (9.6%). The deduced pI value is 12.5 indicating a highly basic protein. Northern blot analysis revealed a 1-kb mRNA highly expressed in brain, trigeminal ganglia and cell lines of neuroendocrine origin. Rabbit polyclonal antiserum raised against a synthetic IA-4 peptide, designated Pep-1, not only reacted with IA-4 recombinant protein, but also immunostained the islets of Langerhans and large neurons of the hippocampus, cerebral cortex, spinal cord, dorsal ganglia and Purkinje cells of the cerebellum. The high expression of IA-4 protein in neuroendocrine cells and its unique amino acid sequence suggest that IA-4 may have an important, but still undetermined, function in these special cell types.
Donadel
G
G
Oral Infection and Immunity Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892-4322, USA.
Marinos
N
N
DeSilva
M G
MG
Lu
J
J
Notkins
A L
AL
Lan
M S
MS
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D015870:Gene Expression; D005982:Glutathione Transferase / Q000235:genetics; D007515:Islets of Langerhans / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics*; D009479:Neuropeptides; D009490:Neurosecretory Systems / Q000737:chemistry; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D011993:Recombinant Fusion Proteins; D012668:Trigeminal Ganglion / Q000737:chemistry; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; C112832:Pcsk1n protein, mouse; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase