Synthesis of a homodimer neurohormone precursor of locust adipokinetic hormone studied by in vitro translation and cDNA cloning.
The homodimer neurohormone precursor P1, consisting of 41 residue subunits or A-chains, is synthesized by the glandular neurosecretory cells of the corpora cardiaca (CC) of the locust Schistocerca gregaria. Processing of P1 generates two copies of a 10 amino acid peptide neurohormone (AKH I) and one copy of a homodimer peptide (APRP 1). Here we show that the P1 dimer is formed from two independent A-chain translation products. Translation of CC mRNA in vitro produces a prominent 6.4 kd protein, the synthesis of which can be blocked by oligonucleotides hybridizing to mRNA encoding the A-chain. Northern blot experiments suggest that the 6.4 kd protein is produced by an integral of 500 base mRNA. cDNA cloning reveals a pre-A-chain structure in which a single copy of the A-chain is preceded by a 22 amino acid signal peptide. This evidence indicates that the P1 dimer is synthesized by coupling of very small translational products rather than by folding and processing of a larger protein containing more than one copy of the A-chain.
Schulz-Aellen
M F
MF
University of Geneva, Laboratoire de Neurobiologie, Switzerland.
Roulet
E
E
Fischer-Lougheed
J
J
O'Shea
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002474:Cell-Free System; D004247:DNA / Q000235:genetics; D004274:DNA, Recombinant; D006110:Grasshoppers / Q000235:genetics / Q000378:metabolism*; D007301:Insect Hormones / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000096:biosynthesis* / Q000235:genetics; D011061:Poly A / Q000235:genetics; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000096:biosynthesis / Q000235:genetics*; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics
D004274:DNA, Recombinant; D007301:Insect Hormones; D009479:Neuropeptides; D011498:Protein Precursors; D012333:RNA, Messenger; D011061:Poly A; C014956:adipokinetic hormone (locust); D004247:DNA