Cloning of two protease genes fromRhodocyclus gelatinosa APR 3-2 and their expression inEscherichia coli

Two different protease genes were cloned fromRhodocyclus gelatinosa APR 3-2 inEscherichia coli HB 101/ with pBR329 or its derivatives. The recombinant plasmids designated as pRP100 and pRP300 contained 11.2 and 10.6 kb DNA fragments, respectively. The differences of both plasmids in restriction enzyme maps indicate that these plasmids contained different protease genes. DNA fragments coding for protease, 6.4 kb and 4.5 kb from pRP100 and pRP300, were subcloned into pRP329 and designated as pRP101 and pRP301, respectively. The two cloned proteases were excreted in culture medium ofE. coli, and ß-lactamase ofE. coli, which was originally localized in periplasmic space, was also excreted in the medium.     

Protection of OK-432, a Streptococcus pyogenes preparation, against lethal infection of mice with herpes simplex virus

We have studied the protective effect of OK-432, a biological response modifier (BRM) of Streptococcus pyogenes origin, on the lethal infection of mice with herpes simplex virus (HSV)-1. A single intraperitoneal (i.p.) injection of more than 10 micrograms of OK-432, when given at least two days before the infection, gave a marked effect yielding nearly 100% protection against ordinarily lethal infection. The protection was independent of the amount of infected virus inoculated. When given after the infection, the agent even at the maximal dose (100 micrograms), produced only a marginal effect. A single i.p. administration of OK-432 augmented the natural killer (NK) activity of peritoneal exudate cells and spleen mononuclear cells in mice 2 to 3 days after injection of OK-432, coinciding with the times when it induced a survival effect on HSV-infection. Treating OK-432-treated mice with a combination of an anti-macrophage agent, silica, and an anti-NK cell agent, anti-asialo GM1 serum, before infection diminished the antiviral effect of OK-432. The OK-432 protection against HSV infection was also markedly diminished in athymic nude mice. Thus, the protective effect of OK-432 on lethal HSV infection seems to be based on the activation of NK cells, macrophages, and T lymphocytes.     

A possible correlation between histological changes in regional subcutaneous tissue induced by bacterial lipopolysaccharides and their adjuvant activities

Previously it was demonstrated that Klebsiella pneumoniae O3 lipopolysaccharide (KO3 LPS) exhibited much stronger adjuvant action on antibody response to subcutaneously (s.c.) injected sheep red blood cells or deaggregated bovine serum albumin than did other kinds of LPS, the R-form LPS lacking the O-specific polysaccharide chain of KO3 LPS (R-LPS), and the lipid A fractionated from KO3 LPS. We compared histological changes in the regional subcutaneous tissues of mice injected subcutaneously (s.c.) with KO3 LPS, the lipid A, and R-LPS. At the early stage after injection, KO3 LPS induced the infiltration of a large number of inflammatory cells, mainly polymorphonuclear leukocytes (PMN), at the site of injection. Neither R-LPS nor the lipid A induced the accumulation of PMN so much as KO3 LPS did. When injected s.c. with LPS from Escherichia coli O111 (EO111 LPS) and O55 (EO55 LPS), and Salmonella enteritidis (Sent LPS), the appearance of PMN at the regional site was much less than KO3 LPS. KO3 LPS could accumulate more 51Cr-labeled leukocytes at the injection site than EO111 LPS and Sent LPS. Administration of acetylsalicylic acid, which can inhibit leukocyte migration in inflammatory lesions, suppressed its adjuvant action. It was therefore suggested that the strong adjuvant action of KO3 LPS in s.c. injection might be dependent on its potent capability of accumulating PMN at the regional subcutaneous tissue. Furthermore, at the late stage after injection, the formation of several lymphoid follicles at the regional site was seen only in mice injected with KO3 LPS. It might be also related to the strong adjuvant action of KO3 LPS.     

Conditionally lethal amber mutations in the leader peptidase gene of Escherichia coli.

The lep gene of Escherichia coli encodes the leader peptidase which cleaves amino-terminal leader sequences of secreted proteins. To facilitate the study of structure-function relationships of the leader peptidase, 22 amber mutations in lep were isolated by localized mutagenesis. These amber mutants grew at 32 degrees C but not at 42 degrees C in the presence of a temperature-sensitive amber suppressor. Most of them were lethal under sup0 conditions. However, one amber mutant, the lep-9 mutant, exhibited temperature-sensitive growth in the sup0 strain, indicating that the amber fragment is active at 32 degrees C but not at 42 degrees C. Protein precursors of the maltose-binding protein and OmpA accumulate strikingly in the lep-9 mutant.     

Purification and characterization of the active serine: pyruvate aminotransferase of rat liver mitochondria expressed in Escherichia coli

In the previous study (Oda, T., et al. (1985) Eur. J. Biochem. 150, 415-421), we isolated a cDNA clone which expressed in Escherichia coli a specific size of product having the activity of rat liver serine:pyruvate aminotransferase (SPTm). This specific product (SPT10) was purified to homogeneity through three different column chromatographies. The amino acid composition and N-terminal amino acid sequence of the purified enzyme agreed with those predicted from the nucleotide sequence of cDNA and showed that SPT10 consists of the whole amino acid sequence of mature SPTm and several extra amino acid residues at the N-terminus. The catalytic and physical properties of SPT10, such as substrate specificity, Km for alpha-keto acids, electric charge, and quaternary structure, were all very similar to those of SPTm. Using several cDNA clones which lack a 5'-terminal sequence corresponding to a portion of the N-terminal amino acid sequence of SPTm, we examined the expression profile of the specific product in bacteria transformed with each cDNA clone. The products encoded by these cDNAs were segregated into inclusion bodies and were neither catalytically active nor easily solubilized by sonication. In contrast, the inclusion bodies were not formed in the bacteria transformed with the cDNA clone for SPT10.     

High levels of human apolipoprotein A-I in transgenic mice result in increased plasma levels of small high density lipoprotein (HDL) particles comparable to human HDL3

Five lines of transgenic mice, which had integrated the human apolipoprotein (apo) A-I gene and various amounts of flanking sequences, were established. Normally, apoA-I is expressed mainly in liver and intestine, but all of the transgenic lines only expressed apoA-I mRNA in liver, strongly suggesting that 256 base pairs of 5'-flanking sequence was sufficient for liver apoA-I gene expression but that 5.5 kilobase pairs was not sufficient for intestinal expression. Mean plasma levels of human apoA-I varied in different lines from approximately 0.1 to 200% of normal mouse levels. This was not dependent on the amount of flanking sequence. Lipoprotein levels were studied in detail in one of the lines with a significantly increased apoA-I pool size. In one study, the total plasma apoA-I level (mouse plus human) was 381 +/- 43 mg/dl in six animals from this line, compared to 153 +/- 17 mg/dl in matched controls. Total and high density lipoprotein cholesterol (HDL-C) levels were increased 60% in transgenic animals, compared to controls (total cholesterol: 125 +/- 12 versus 78 +/- 13 mg/dl, p = 0.0001; HDL-C 90 +/- 7 versus 55 +/- 11 mg/dl, p = 0.0001). The molar ratio of HDL-C/apoA-I was significantly lower in transgenic animals, 17 +/- 1 versus 25 +/- 2 (p = 0.0001), suggesting the increase was in smaller HDL particles. This was confirmed by native gradient gel electrophoresis. This was not due to aberrant metabolism of human apoA-I in the mouse, since human apoA-I was distributed throughout the HDL particle size range and was catabolized at the same rate as mouse apoA-I. In another study of 23 transgenic mice, HDL-C and human apoA-I levels were highly correlated (r = 0.87, p less than 0.001). The slope of the correlation line also indicated the additional HDL particles were in the smaller size range. We conclude that human apoA-I can be incorporated into mouse HDL, and excessive amounts increase HDL-C levels primarily by increasing smaller HDL particles, comparable to human HDL3 (HDL-C/apoA-I molar ratio = 18).     

Amino acid residues stabilizing a Bacillus alpha-amylase against irreversible thermoinactivation

The alpha-amylase of Bacillus licheniformis (BLA) is stable and active at high temperature. More than 80% of its activity is retained after heat treatment at 90 degrees C for 30 min, and the optimum temperature for its activity is 80-85 degrees C. In contrast, the alpha-amylase of Bacillus amyloliquefaciens (BAA), the amino acid sequence of which shows 80% homology with that of BLA, is rapidly inactivated at 90 degrees C. Various chimeric genes were constructed from the structural genes for the two enzymes, and their products were analyzed for stability as to irreversible thermoinactivation. Two regions in the amino acid sequence of BLA comprising Gln178 (region I) and the 255th-270th residues (region II), respectively, were shown to determine the thermostability of BLA. Region I plays a major role in determining the thermostability. By means of site-directed mutagenesis of the BAA gene, deletion of Arg176 and Gly177 in region I and substitutions of alanine for Lys269 and aspartic acid for Asn266 in region II were shown to be responsible for the enhancement of the thermostability. Mutant BAAs containing the above deletion and substitutions showed almost the same thermostability as BLA as to irreversible thermoinactivation. Nevertheless, the mutant BAAs showed a temperature optimum as low as that of BAA (65 degrees C), indicating that they are still susceptible to reversible inactivation at temperatures higher than 65 degrees C.     

Identification in turkey gizzard of an acidic protein related to the C-terminal portion of smooth muscle myosin light chain kinase

The isolation of an acidic protein, pI 4.5, that is abundant in turkey gizzard is described. Its apparent molecular weight measured by electrophoretic procedures is 24,000. This protein is phosphorylated by the catalytic subunit of the cAMP-dependent protein kinase and one phosphorylation site is indicated. From sequence determinations of tryptic peptides it is concluded that this protein is closely related to the C-terminal part of smooth muscle myosin light chain kinase. The initiation site for the protein is to the C-terminal side of the calmodulin-binding site. From the sequence data an estimated molecular weight is 18,000. This protein is expressed independently, as indicated by a blocked N terminus, and is probably the translation product of the 2.7-kilobase RNA detected previously in chicken gizzard (Guerriero, V., Jr., Russo, M. A., Olson, N. J., Putkey, J. A., and Means, A. R. (1986) Biochemistry 25, 8372-8381). Because of its putative origin as the C-terminal end of smooth muscle myosin light chain kinase, it is termed "telokin" (from a combination of kinase and the Greek telos, "end").     

Decrease of nitrate biosynthesis in scorbutic mutant rats unable to synthesize ascorbic acid

The effect of ascorbic acid deficiency on the urinary excretion of nitrate was investigated using a mutant strain of rats (osteogenic disorder syndrome rats; ODS rats) unable to synthesize ascorbic acid. The amount of urinary nitrate excreted by ODS rats with or without ascorbic acid supplementation were measured before and after the intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS). Urinary nitrate excretion increased markedly after LPS injection. Urinary nitrate excretion by ODS rats not supplied with ascorbic acid was significantly less than that of those supplied with ascorbic acid both before and after LPS injection. These results show that ascorbic acid enhances both LPS-stimulated and constitutive nitrate production in vivo.