Construction of a human cytochrome c gene and its functional expression in Saccharomyces cerevisiae

The nucleotide sequences of a partial cDNA and three pseudogenes of human cytochrome c were determined. The complete nucleotide sequences which encode human cytochrome c were constructed on the basis of one of the pseudogenes by in vitro mutagenesis. The constructed human cytochrome c was functionally expressed in Saccharomyces cerevisiae. The recombinant human cytochrome c was purified and characterized.     

Sequences of cDNAs for human salivary and pancreatic α-amylases

The nucleotide sequences of the cloned human salivary and pancreatic α-amylase cDNAs correspond to the continuous mRNA sequences of 1768 and 1566 nucleotides, respectively. These include all of the amino acid coding regions. Salivary cDNA contains 200 bp in the 5′-noncoding region and 32 in the 3′-noncoding region. Pancreatic cDNA contains 3 and 27 bp of 5′- and 3′-noncoding regions, respectively. The nucleotide sequence humology of the two cDNAs is 96% in the coding region, and the predicted amino acid sequences are 94% homologous.Comparison of the sequences of human α-amylase cDNAs with those previously obtained for mouse α-amylase genes (Hagenbuchle et al., 1980; Schibler et al., 1982) showed the possibility of gene conversion between the two genes of human α-amylase.     

Purification of hepatitis B virus gene X product synthesized in Escherichia coli and its detection in a human hepatoblastoma cell line producing hepatitis B virus

A fused gene containing 94% of the hepatitis B virus (HBV) open reading frame X was expressed in Escherichia coli, and its 17-kDa product was purified by ion-exchange chromatography. Antibody elicited against the X-gene product reacted with materials proximal to the nuclear membrane of a human hepatoblastoma cell line producing HBV particles. No such reaction was observed with the same cell line that did not produce HBV particles.     

Expression of hepatitis B virus middle and large surface antigen genes in Saccharomyces cerevisiae.

The hepatitis B virus genome carries the surface antigen (SAg) gene and an open reading frame that encodes two SAg-related polypeptides: SAg with a 55-amino-acid N-terminal extension polypeptide and SAg with a 174-amino-acid N-terminal extension polypeptide. These are termed middle S and large S, respectively. These polypeptides or their glycosylated derivatives have been detected in Dane particles, but their chemical and biological properties have remained largely unknown because of their limited availability. We attempted to produce these proteins in Saccharomyces cerevisiae by placing the coding regions under the control of the promoter of the yeast glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene. Yeast cells carrying middle S and large S coding sequences produced 33,000- and 42,000-dalton products, respectively, each of which reacted with anti-S antibody and bound to polymerized human serum albumin, in accordance with the known properties of pre-S proteins from particles in human sera (K. H. Heermann, U. Goldmann, W. Schwartz, T. Seyffarth, H. Baumgarten, and W. H. Gerlich, J. Virol. 52:396-402, 1984; A. Machida, S. Kishimoto, H. Ohnuma, K. Baba, Y. Ito, H. Miyamoto, G. Funatsu, K. Oda, S. Usuda, S. Togami, T. Nakamura, Y. Miyakawa, and M. Mayumi, Gastroenterology 86:910-918, 1984). The middle S polypeptide is glycosylated and can be assembled into particles whose size and density are similar to those of SAg. However, this polypeptide was highly susceptible to proteolytic degradation into 29,000- and 26,000-dalton polypeptides, of which only the former retained the binding activity to polymerized albumin. The large S polypeptides are nonglycosylated, relatively stable, and do not seem to assemble into particles by themselves.     

A carboxyl-terminal hydrophobic region of yeast cytochrome c1 is necessary for functional assembly into complex III of the respiratory chain

Cytochrome c1 is an amphiphilic protein which binds to the mitochondrial inner membrane, presumably through a hydrophobic region near the carboxyl (C)-terminus. In the preceding study (Hase, T., et al. (1987) J. Biochem. 102, 401-410), two cytochrome c1 mutations were constructed: delta 1 and delta 2 cytochromes c1, in which the C-terminal segments of 17 and 71 residues were replaced by foreign sequences of 20 and 15 residues, respectively. delta 2 cytochrome c1 had lost the putative membrane anchor. The two cytochrome c1 mutants were localized in mitochondria, but succinate-cytochrome c1 reductase activity was detected only in the mitochondria containing delta 1 cytochrome c1. The membrane association of the two mutant molecules as well as that of authentic cytochrome c1 was investigated. These three molecules were firmly attached to mitochondrial membranes and not solubilized on either sonication or sodium carbonate (pH 11) treatment. However, when the membranes were solubilized with Triton X-100, both the delta 1 and authentic cytochromes c1 were extracted from the membranes more easily than delta 2 cytochrome c1. By fractionating cholate extracts of mitochondrial membranes with ammonium sulfate, delta 1 cytochrome c1 was cofractionated with the enzymatic activity of complex III, but delta 2 cytochrome c1 was clearly separated from the complex III fraction. Trypsin treatment of mitochondria and mitoplasts showed that delta 2 cytochrome c1 was exposed to the intermembrane space, with such a topology that its trypsin susceptibility became much higher than that of the authentic molecule.(ABSTRACT TRUNCATED AT 250 WORDS)     

Molecular cloning and nucleotide sequence of cDNA encoding the entire precursor of rat liver medium chain acyl coenzyme A dehydrogenase

cDNA encoding the precursor of rat liver medium chain acyl-CoA dehydrogenase (EC 1.3.99.3) was cloned and sequenced. The longest cDNA insert isolated was 1866 bases in length. This cDNA encodes the entire protein of 421-amino acids including a 25-amino acid leader peptide and a 396-amino acid mature polypeptide. The identity of the medium chain acyl-CoA dehydrogenase clone was confirmed by matching the amino acid sequence predicted from the cDNA to the NH2-terminal and nine internal tryptic peptide sequences derived from pure rat liver medium chain acyl-CoA dehydrogenase. The calculated molecular masses of the precursor medium chain acyl-CoA dehydrogenase, the mature medium chain acyl-CoA dehydrogenase, and the leader peptide are 46,600, 43,700, and 2,900 daltons, respectively. The leader peptide contains five basic amino acids and only one acidic amino acid; thus, it is positively charged, overall. Cysteine residues are unevenly distributed in the mature portion of the protein; five of six are found within the NH2-terminal half of the polypeptide. Comparison of medium chain acyl-CoA dehydrogenase sequence to other flavoproteins and enzymes which act on coenzyme A ester substrates did not lead to unambiguous identification of a possible FAD-binding site nor a coenzyme A-binding domain. The sequencing of other homologous acyl-CoA dehydrogenases will be informative in this regard.     

Identification of a novel alpha-amylase by expression of a newly cloned human amy3 cDNA in yeast

A novel amylase gene (amy3) that differs in nucleotide sequence from salivary amylase gene (amy1) and pancreatic amylase gene (amy2) has been described [Tomita et al., Gene 76 (1989) 11-18], but whether this gene can ever code for an active enzyme has not been shown. We prepared cDNA of this gene from an mRNA obtained from lung carcinoid tissue, and expressed it in Saccharomyces cerevisiae under the control of an acid phosphatase promoter. The product was secreted into culture media, and showed enzymatic activity, demonstrating that this novel alpha-amylase gene (amy3) can code for a functional isozyme. We purified this enzyme, and compared its biological properties with those of salivary and pancreatic human amylases similarly expressed in yeast. We observed that the novel amylase isozyme is more heat-sensitive than others, and that its substrate specificity is different from the other two isozymes.     

Regional localization of the LCA oncogene to human chromosome region 2q14----q21

A novel human oncogene, LCA, was assigned to region 2q14----q21 by in situ molecular hybridization. The present regional mapping substantiates the previous assignment that was performed by Southern blot analyses of DNAs from flow-sorted human chromosomes and human-mouse somatic cell hybrids.