Hepatocyte growth factor (HGF) is the most potent mitogen for mature parenchymal hepatocytes in primary culture, and seems to be a hepatotrophic factor that acts as a trigger for liver regeneration after partial hepatectomy and liver injury. The partial purification and characterization of HGF have been reported. We have demonstrated that pure HGF from rat platelets is a new growth factor effective at concentrations as low as 1 ng ml-1. The effects of HGF and epidermal growth factor (EGF) are additive. The activity of HGF is not species-specific, although it does not stimulate growth in Swiss 3T3 fibroblasts. HGF has a relative molecular mass (Mr) of 82,000 and is a heterodimer composed of a large alpha-subunit of Mr 69,000 and a small beta-subunit of Mr 34,000. Here we report the amino-acid sequence of human HGF determined by complementary DNA cloning and the expression of biologically active human HGF from COS-1 cells transfected with cloned cDNA. The nucleotide sequence of the human HGF cDNA reveals that both alpha- and beta-chains are contained in a single open reading frame coding for a pre-pro precursor protein of 728 amino acids.

Cloning and sequence analysis of cDNA for the Electrophorus electricus electroplax sodium channel indicate that this protein, consisting of 1,820 amino acid residues, exhibits four repeated homology units, which are presumably oriented in a pseudosymmetric fashion across the membrane. Each homology unit contains a unique segment with clustered positively charged residues, which may be involved in the gating structure, possibly in conjunction with negatively charged residues clustered elsewhere.

The primary structure of rat hepatocyte growth factor (HGF) was elucidated by determining the base sequence of the complementary DNA (cDNA) of HGF. The cDNA for rat HGF was isolated by screening a liver cDNA library with oligonucleotides based on the partial N-terminal amino acid sequence ofthe P subunit ofpurified rat HGF. HGF is encoded in an mRNA of about 6 kilobases. Both a and 13 subunits of HGF are specified in a single open reading frame for a 728-amino acid protein with a calculated molecular weight of 82,904. The N-terminal part of HGF has a signal sequence and a prosequence with 30 and 25 amino acid residues, respectively. The mature heterodimer structure is derived proteolytically from this single pre-pro precursor polypeptide. The calculated molecular weights of the a and (3 subunits are 50,664 and 25,883, respectively, and each subunit has two potential N-lked glycosylation sites. The amino acid sequence of HGF is 38% identical with that of plasminogen. The a subunit of HGF contains four "Ikringle" structures, and the (3 subunit has 37% amino acid identity with the serine protease domain of plasmin. Northern blot analysis revealed that HGF mRNA was expressed in rat various tissues, including the liver, kidney, lung, and brain.were shown to be markedly elevated in the blood plasma of rats with hepatitis induced by administration ofa hepatotoxin such as CC14 or D-galactosamine (18). In humans, similar findings were observed in the sera of patients after partial hepatectomy (19) and with fulminant hepatitis (33).HGF has been isolated as a homogeneous material from rat platelets and shown to be a heat-labile protein of -82 kDa, composed of a 69-kDa a subunit and a 34-kDa (3 subunit (20,21). HGF at 1 ng/ml markedly stimulated DNA synthesis in adult rat hepatocytes and its effect was additive or synergistic with those of insulin and epidermal growth factor. HGF has no species specificity; for example, rat HGF also stimulated DNA synthesis in human, canine, and porcine hepatocytes in primary culture. In contrast, HGF did not stimulate DNA synthesis in established cell lines such as Swiss mouse 3T3 fibroblasts and BRL (buffalo rat liver) epithelial cells.Here we report the complete amino acid sequence of rat HGF obtained by cloning and sequence analysis of its cDNA. § We have found that HGF mRNA is expressed in various rat tissues including the kidney, heart, lung, and brain, as well as in injured liver.Liver regenerates actively after partial hepatectomy and liver injury. Early investigations (1-4) showed that hepatotrophic factors existed in the blood of partially hepatectomized animals. However, no one succeeded in purifying and characterizing such a humoral factor until recently, largely because no simple, reproducible, and sensitive assay for the factor has been available.Although many in vitro experimental methods using established liver and hepatoma cell lines have been employed in attempts to identify the hepatotrophic factor, these assays are unsuitable because these cell lines have lost al...

The nicotinic acetylcholine receptor (AChR) from fish electric organ is well characterized and is known to consist of five subunits present in a molar stoichiometry of alpha 2 beta gamma delta (reviewed in refs 1-3). The mammalian skeletal muscle AChR is thought to have a similar subunit structure. We have recently elucidated the primary structures of the alpha-, beta-, gamma- and delta-subunit precursors of the Torpedo californica AChR by cloning and sequencing cDNAs for these polypeptides; cDNA sequences for the gamma-subunit precursor of the T. californica AChR and the alpha-subunit precursor of the Torpedo marmorata AChR have also been reported by other groups. The four subunits exhibit conspicuous sequence homology and are similar in hydrophilicity profile and predicted secondary structure, thus being most probably oriented in a pseudosymmetric fashion across the membrane. The transmembrane topology of the subunit molecules and the locations of functionally important regions, such as the acetylcholine binding site and the trans-membrane segments which may be involved in the ionic channel, have been proposed. We have now cloned cDNA for the alpha-subunit precursor of the calf skeletal muscle AChR and a human genomic DNA segment containing the corresponding gene. Nucleotide sequence analysis of the cloned DNAs has revealed the primary structures of the calf and human AChR alpha-subunit precursors, which exhibit marked sequence homology with their Torpedo counterpart. The protein-coding sequence of the human AChR alpha-subunit precursor gene is divided by eight introns into nine exons, which seem to correspond to different structural and functional domains of the subunit precursor molecule.

No abstract