Phosphorylation of native 97-kDa 3-hydroxy-3-methylglutaryl-coenzyme A reductase from rat liver. Impact on activity and degradation of the enzyme

Immunoprecipitation of native rat liver microsomal 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, phosphorylated by [gamma-32P]ATP in the presence of reductase kinase, revealed a major 97-kDa 32P band which disappeared upon competition with pure unlabeled 53-kDa HMG-CoA reductase. A linear correlation between the expressed/total HMG-CoA reductase activity ratio (E/T) and the fraction of 32P released from the 97-kDa enzyme established the validity of the E/T ratio as an index of HMG-CoA reductase phosphorylation state in isolated microsomes. Incubation of rat hepatocytes with mevalonolactone resulted in a rapid increase in phosphorylation of microsomal reductase (decrease in E/T) followed by an enhanced rate of decay of total reductase activity which was proportional to the loss of 97-kDa enzyme mass determined by immunoblots. Inhibitors of lysosome function dampened both basal and mevalonate-induced reductase degradation in hepatocytes. In an in vitro system using the calcium-dependent protease calpain-2, up to 5-fold greater yields of soluble 52-56-kDa fragments of reductase (immunoblot and total activity) were obtained when the substrate 97-kDa reductase was phosphorylated before proteolysis. Immunoblots of unlabeled phosphorylated reductase compared with gels of immunoprecipitated 32P-labeled reductase resolved a 52-56-kDa doublet which contained 32P solely in the upper band. These data suggest that a major phosphorylation site of HMG-CoA reductase lies within the "linker" segment joining the membrane spanning and cytoplasmic domains of the native 97-kDa protein.     

The roles of nitrate,photosynthesis and protein turnover in the formation of nitrate reductase in the nit A mutant of Chlamydomonas

The appearance of nitrate reductase activity in derepressed cultures of the Nit A mutant of Chlamydomonas reinhardtii required concomitant photosynthetic CO₂ fixation and was inhibited when protein turnover was prevented. Provided leupeptin was included in the extraction buffer, a single species of nitrate reductase (molecular mass, m = 390 kDa) was extracted from Nit A cultures incubated in nitrate medium for 4 h. Cultures of the mutant incubated in nitrate-free medium contained a number of nitrate reductase species (m = 52–500 kDa). This evidence suggests that nitrate plays a role in the stabilisation of the structure of the mutant nitrate reductase. Only one species of nitrate reductase (m = 188 kDa) was extracted from wild type cultures grown with nitrate.     

Polypeptide composition and an immunological analysis of DNA methyltransferases from different species

The cross-reactivity of the monoclonal anti-human placental DNA methyltransferase antibody M2B10 with DNA methyltransferases isolated from other species was investigated. This antibody immunoprecipitates DNA methyltransferases from mammalian cells, i.e., human placenta, mouse P815 cells, and rat liver cells. No cross-reactivity is observed with DNA methyltransferases from wheat germ and with bacterial DNA methyltransferases HpaII and EcoRI. The mammalian enzymes are characterized by polypeptides of molecular mass 150-190 kDa. Polypeptides smaller than 190 kDa are presumably generated by proteolysis of the native 190-kDa DNA methyltransferase. Trypsin digestion of the 190-kDa polypeptide isolated from mouse cells results in progressive appearance of DNA methyltransferase polypeptides of 150-190, 110, 100, and 52-60 kDa.     

Phosphate induced swelling, inhibition and partial uncoupling of oxidative phosphorylation in heart mitochondria in the absence of external calcium and the presence of EGTA

Short-term (0–1 h) incubations of rat hepatocytes with oleate (2 mM) resulted in a decrease in the rate of cholesterol synthesis compared to controls incubated in the absence of fatty acid. However, during this period the activity of hydroxy-methylglutaryl coenzyme A (HMG-CoA) reductase was higher in the oleate-incubated cells. After longer incubation periods in the presence of oleate there was a higher rate of cholesterol synthesis than in the corresponding non-oleate controls and HMG-CoA reductase activity remained elevated. This biphasic effect provides an explanation for previous contradictory reports concerning the effect of exogenous fatty acids on the rate of cholesterol synthesis in liver. The present studies also suggest that in some physiological situations, the rate of cholesterol synthesis is determined by substrate supply rather than by HMG-CoA reductase activity.     

Isolation of a soluble and membrane-associated Fe(III) reductase from the thermophile, Thermus scotoductus (SA-01)

The Fe(III) reductase activity was studied in the South African Fe(III)-reducing bacterium, Thermus scotoductus (SA-01). Fractionation studies revealed that the membrane as well as the soluble fraction contained NAD(P)H-dependent Fe(III) reductase activity. The membrane-associated enzyme was solubilized by KCl treatment and purified to electrophoretic homogeneity by hydrophobic interaction chromatography. A combination of ion-exchange and gel filtration chromatography was used to purify the soluble enzyme to apparent homogeneity. The molecular mass of the membrane-associated Fe(III) reductase was estimated to be 49 kDa, whereas the soluble Fe(III) reductase had an apparent molecular mass of 37 kDa. Optimum activity for the membrane-associated enzyme was observed at around 75 degrees C, whereas the soluble enzyme exhibited a temperature optimum at 60 degrees C.     

Differential reactivity of filarial antigens with human sera from bancroftian filariasis endemic zone

The reacting pattern of circulating filarial antigen fraction-2 fromWuchereria bancrofti and soluble antigen from adultBrugia malayi with bancroftian filarial sera were analysed by immunoblotting technique and enzyme linked immunosorbent assay. Microfilaraemic sera reacted specifically with proteins of molecular weight 200, 120, 97, 56, 54, 43, 26 and 17 kDa of circulating Filarial antigen fraction-2 and 44, 40, 38, 31, 22 and 18 kDa ofBrugia malayi adult soluble antigen. Clinical filarial sera identified protein molecules of 56, 54 and 42 kDa of circulating filarial antigen fraction-2 and 19, 16 and 14 kDa ofBrugia malayi adult soluble antigen. Some components of both the antigen preparation were also identified by endemic normal serai.e.proteins 120, 97, 62, 43 and 33 kDa of circulating filarial antigen fraction-2 and 170, 120, 43, 31 and 12 kDa ofBrugia malayi adult soluble antigen. One of the sodium dodecyl sulphate-polyacrylamide gel electropherosis fractions of circulating filarial antigen fraction-2 (CFA₂-8) andBrugia malayi adult soluble antigen fraction-6 when used in enzyme linked immunosorbent assay could differentiate microfilaraemic sera from endemic normal and clinical filarial sera. The other antigen fractions (CFA₂-2, 6 and 7 andBmA-2) showed a high geometric mean titre of filarial immunoglobulin G antibodies in endemic normal sera when compared to microfilaraemia and clinical filarial sera. These proteins need to be further studied to assess their involvement in protecting from filarial infection in an endemic area.     

Characterization, size estimation and solubilization of α-macroglobulin complex receptors in liver membranes

Receptors for α₂-macroglobulin-proteinase complexes have been characterized in rat and human liver membranes. The affinity for binding of ¹²⁵I-labelled α₂-macroglobulin · trypsin to rat liver membranes was markedly pH-dependent in the physiological range with maximum binding at pH 7.8–9.0. The half-time for association was about 5 min at 37°C in contrast to about 5 h at 4°C. The half-saturation constant was about 100 pM at 4°C and 1 nM at 37°C (pH 7.8). The binding capacity was approx. 300 pmol per g protein for rat liver membranes and about 100 pmol per g for human membranes. Radiation inactivation studies showed a target size of 466 ± 71 kDa (S.D., n = 7) for α₂-macroglobulin · trypsin binding activity. Affinity cross-linking to rat and human membranes of ¹²⁵I-labelled rat α₁-inhibitor-3 · chymotrypsin, a 210 kDa analogue which binds to the α₂-macroglobulin receptors in hepatocytes (Gliemann, J. and Sottrup-Jensen, L. (1987) FEBS Lett. 221, 55–60), followed by SDS-polyacrylamide gel electrophoresis, revealed radioactivity in a band not distinguishable from that of cross-linked α₂-macroglobulin (720 kDa). This radioactivity was absent when membranes with bound ¹²⁵I-α₁-inhibitor-3 complex were treated with EDTA before cross-linking and when incubation and cross-linking were carried out in the presence of a saturating concentration of unlabelled complex. The saturable binding activity was maintained when membranes were solubilized in the detergent 3-[(3-cholamidopropyl)dimethylammonio]profane sulfonate (CHAPS) and the size of the receptor as estimated by cross-linking experiments was shown to be similar to that determined in the membranes. It is concluded that liver membranes contain high concentrations of an approx. 400–500 kDa α₂-macroglobulin receptor soluble in CHAPS. The soluble preparation should provide a suitable material for purification and further characterization of the receptor.     

Characterization, size estimation and solubilization of alpha-macroglobulin complex receptors in liver membranes

Receptors for alpha 2-macroglobulin-proteinase complexes have been characterized in rat and human liver membranes. The affinity for binding of 125I-labelled alpha 2-macroglobulin.trypsin to rat liver membranes was markedly pH-dependent in the physiological range with maximum binding at pH 7.8-9.0. The half-time for association was about 5 min at 37 degrees C in contrast to about 5 h at 4 degrees C. The half-saturation constant was about 100 pM at 4 degrees C and 1 nM at 37 degrees C (pH 7.8). The binding capacity was approx. 300 pmol per g protein for rat liver membranes and about 100 pmol per g for human membranes. Radiation inactivation studies showed a target size of 466 +/- 71 kDa (S.D., n = 7) for alpha 2-macroglobulin.trypsin binding activity. Affinity cross-linking to rat and human membranes of 125I-labelled rat alpha 1-inhibitor-3.chymotrypsin, a 210 kDa analogue which binds to the alpha 2-macroglobulin receptors in hepatocytes (Gliemann, J. and Sottrup-Jensen, L. (1987) FEBS Lett. 221, 55-60), followed by SDS-polyacrylamide gel electrophoresis, revealed radioactivity in a band not distinguishable from that of cross-linked alpha 2-macroglobulin (720 kDa). This radioactivity was absent when membranes with bound 125I-alpha 1-inhibitor-3 complex were treated with EDTA before cross-linking and when incubation and cross-linking were carried out in the presence of a saturating concentration of unlabelled complex. The saturable binding activity was maintained when membranes were solubilized in the detergent 3-[(3-cholamidopropyl)dimethylammonio]propane sulfonate (CHAPS) and the size of the receptor as estimated by cross-linking experiments was shown to be similar to that determined in the membranes. It is concluded that liver membranes contain high concentrations of an approx. 400-500 kDa alpha 2-macroglobulin receptor soluble in CHAPS. The soluble preparation should provide a suitable material for purification and further characterization of the receptor.     

Altered kinetic properties of rat liver 3-hydroxy-3-methylglutaryl coenzyme A reductase following dietary manipulations

The microsomal enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase catalyzes the rate-limiting step in the cholesterogenic pathway and was proposed to be composed in situ of 2 noncovalently linked subunits (Edwards, P.A., Kempner, E.S., Lan, S.-F., and Erickson, S.K. (1985) J. Biol. Chem. 260, 10278-10282). In the present report, the activities and kinetic properties of HMG-CoA reductase in microsomes isolated from livers of rats fed on diets supplemented with either ground Amberlite XAD-2 ("X"), cholestyramine/mevinolin ("CM"), or unsupplemented, normal rat chow ("N"), were compared. The specific activities of HMG-CoA reductase in X and CM microsomes were, respectively, 5- and 83-fold higher than that of N microsomes. In NADPH-dependent kinetics of HMG-CoA reductase activated with 4.5 mM GSH, the concentration of NADPH required for half-maximal velocity (S0.5) was 209 +/- 23, 76 +/- 23, and 40 +/- 4 microM for the N, X, and CM microsomes, respectively. While reductase from X microsomes displays cooperative kinetics toward NADPH (Hill coefficient (nH) = 1.97 +/- 0.07), the enzyme from CM microsomes does not (nH = 1.04 +/- 0.07). Similarly to HMG-CoA reductase from CM microsomes, the freeze-thaw solubilized enzyme ("SOL") displays no cooperativity toward NADPH and its Km for this substrate is 34 microM. At 4.5 mM GSH, HMG-CoA reductase from X, CM, and SOL preparations has a similar Km value for [DL]-HMG-CoA, ranging between 13-16 microM, while reductase from N microsomes had a higher Km value (42 microM) for this substrate. No cooperativity towards HMG-CoA was observed in any of the tested enzyme preparations. Immunoblotting analyses of the different preparations demonstrated that the observed altered kinetics of HMG-CoA reductase in the microsomes is not due to preferential proteolytic cleavage of the native 97-100 kDa subunit of the enzyme to the noncooperative 50-55 kDa species. Moreover, it was found that the ratio enzymatic activity/immunoreactivity of the reductase increased in the order N less than X less than CM approximately equal to SOL, indicating that the activity per reductase molecule increases with the induction of the enzyme. These results are compatible with a model suggesting that dietary induction of hepatic HMG-CoA reductase may change the state of functional aggregation of its subunits.     

Isolation and purification of a rat liver 3-hydroxy-3-methylglutaryl-coenzyme reductase activating protein (RAP)

A protein with an estimated subunit mass of 19 kDa was isolated and purified from perfused rat liver cytosol. This protein activates hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase (NADPH) (EC 1.1.1.34), the rate-limiting enzyme in the cholesterol biosynthetic pathway. The activation process by this HMG-CoA reductase activating protein (RAP) is time-dependent and requires NADPH. Maximal activity of HMG-CoA reductase induced by RAP is comparable to that obtained in the presence of thiols, such as GSH, and can exceed 100-fold the activity obtained when thiols are omitted. Purified RAP lacks ability to reduce 5,5'-dithiobis-(2-nitrobenzoic acid). RAP was purified to homogeneity utilizing DEAE- and phenyl-Sepharose CL-4B column chromatography. The purified RAP migrates as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and shows multiple interconvertible aggregational forms on native polyacrylamide gel electrophoresis. A monospecific antibody against RAP was prepared by immunization of hens and extracted from either their egg yolks or serum. The catalytic activity of RAP might be responsible for the physiological activation of HMG-CoA reductase and regulation of its activity.     

Influence of nitrogen supply and sink strength on changes in leaf nitrogen compounds during senescence in two wheat cultivars

Changes in various nitrogen compounds during senescence of the fourth leaf were studied in two cultivars of spring wheat (Triticum aestivum L.). One of the cultivars (Yecora) was supplied with two N levels; the other (Tauro) was grown with the high N level and pruned above the fourth leaf, whereas the control was left intact. In both cultivars grown with high N supply, net nitrogen export from the fourth leaf did not occur until 35 days after sowing (DAS). Loss of leaf soluble proteins started earlier than that of chlorophylis, and coincided initially with an increase in insoluble protein. In N deficient plants the level of total N, soluble protein, and the activity of nitrate reductase (NRA. EC 1.6.6.1) started to decrease about 5 days earlier, and along with chlorophyll, continued to decrease at a faster rate, than in high N plants. Also, with low N supply, the large subunit (LSU, 58 kDa) of ribulose-1.5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) decreased in greater proportion than other soluble proteins, while with high N supply the decrease in Rubisco LSU was similar to that of other soluble proteins. Nitrogen deficiency caused a greater decrease in soluble proteins than in insoluble proteins, and NRA relative to soluble proteins. The faster senescing Tauro cultivar had lower levels of most parameters, especially NRA, soluble protein and, after 35 DAS. Rubisco LSU as a proportion of soluble protein. The decrease in sink strength due to shoot pruning did generally not affect the level of the various nitrogenous compounds until 35 DAS; thereafter the levels of most parameters, especially soluble protein, Rubisco LSU and, at late stages of senescence, insoluble protein, were higher in pruned than in control shoots. Thus, shoot pruning slows down senescence. The 56- and 78-kDa polypeptides increased, rather than decreased, with leaf age; the level of these two polypeptides showed a negative relationship with Rubisco LSU (r = -0.933 and r = -0.758, respectively).     

The purification of a detergent-soluble glucose-6-phosphatase from rat liver.

A highly active and soluble glucose-6-phosphatase has been purified to near homogeneity from rat liver. Successful purification has been initiated by covalent labeling of the enzyme in native rat liver microsomes with pyridoxal 5'-phosphate and NaBH4, followed by solubilization of the microsomes with Triton X-100, chromatography on phenyl-Sepharose, hydroxyapatite, DEAE-Sephacel and a second chromatography step on hydroxyapatite. The final enzyme preparation obtained was approximately 700-fold purified over the activity of starting microsomes. As judged by SDS/PAGE the purified glucose-6-phosphatase is composed of a single protein with a molecular mass of 35 kDa. The present work demonstrates that the purified glucose-6-phosphatase must be arranged in the native microsomal membrane so that it is accessible to pyridoxal 5'-phosphate from the cytoplasmic side.     

Comparison of biochemical properties of DNA-topoisomerase I from normal and regenerating liver.

Biochemical properties of topoisomerase I from normal and regenerating rat liver were analysed using crude or fractionated nuclear extracts. We could not detect significative change in topoisomerase I content or activity (magnesium stimulation and inhibition by ATP) during the course of liver regeneration. Topoisomerase I can be resolved into two species of 97 kDa and 100 kDa, with the same pI of 8.2-8.6 as shown by two dimensional gel electrophoresis. The two polypeptides contained a non-phosphorylated precursor and others forms with variable degrees of phosphorylation. In-vitro dephosphorylation with alkaline phosphatase leads to the disappearance of the phosphorylated forms and inactivation of the enzyme. The affinity of topoisomerase I for chromatin (measured by salt elution) differs markedly between normal and regenerating liver: nearly 50% of topoisomerase I remained bound to the chromatin from normal liver at 250 mM NaCl whereas it was completely eluted from 24-h-regenerating-liver nuclei. The biological significance of these results is discussed.     

Intracellular degradation of poly(3-hydroxybutyrate) granules of Zoogloea ramigera I-16-M

Abstract Intracellular degradation of poly(3-hydroxybutyrate) (PHB) in bacteria is not yet clear. The properties of the autodigestion of native PHB granules from Zooglea ramigera I-16-M were examined. The release of d (−)-3-hydroxybutyrate was observed only at pH values higher than about 8.5 and at relatively high ionic strength (optimal concentration 200 mM NaCl). Triton X-100 and diisopropylfluorophosphate inhibited this reaction. Addition of the supernatant fraction of Z. ramigera did not increase the release of d (−)-3-hydroxybutyrate from the native PHB granules. On the other hand, using the protease-treated PHB granules from Alcaligenes eutrophus as a substrate, PHB depolymerase activity was detected in the supernatant fraction of Z. ramigera cells. The soluble PHB depolymerase showed similar properties to the enzyme in the PHB granules. Since PHB depolymerase activity was found in fractions containing d (−)-3-hydroxybutyrate oligomer hydrolase activity, which were separated by DEAE-Toyopearl or by Sephacryl S-100, it is possible that the intracellular PHB depolymerase is identical to the oligomer hydrolase which has been purified already.     

Differential translational effects of myristic acid and eicosapentaenoic acid on 3-hydroxy-3-methylglutaryl-CoA reductase from Reuber H35 hepatoma cells

The mechanisms by which saturated and polyunsaturated fatty acids may exert their effects on levels of blood cholesterol and human atherosclerosis have not been fully established. In this work, we studied the translational effects of myristic (14:0) and eicosapentaenoic (20:5) acids on 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase from Reuber H35 hepatoma cells. This enzyme is an intrinsic membrane, 96-kDa protein whose proteolysis releases an enzymatically active, 52- to 56-kDa, soluble fragment. We optimized an immunoblot procedure for quantifying small amounts of both the native and the soluble forms of HMG-CoA reductase from Reuber H35 hepatoma cells. We demonstrated that the upregulation of HMG-CoA reductase by a acid is due to an increase of the HMG-CoA reductase protein; therefore, protein synthesis would be required for the increase of HMG-CoA reductase activity caused by this fatty acid. In contrast, the downregulation of HMG-CoA reductase caused by eicosapentaenoic acid is not due to decreased protein synthesis, since similar levels of protein were found in the presence and absence of this fatty acid. Results obtained with cycloheximide as a protein-synthesis inhibitor confirm these findings.     

Production of a recombinant hybrid hemoflavoprotein: engineering a functional NADH:cytochrome c reductase.

A gene has been constructed coding for a unique fusion protein, NADH:cytochrome c reductase, that comprises the soluble heme-containing domain of rat hepatic cytochrome b(5) as the amino-terminal portion of the protein and the soluble flavin-containing domain of rat hepatic cytochrome b(5) reductase as the carboxyl terminus. The gene has been expressed in Escherichia coli resulting in the highly efficient production of a functional hybrid hemoflavoprotein which has been purified to homogeneity by a combination of ammonium sulfate precipitation, affinity chromatography on 5'-ADP agarose, and size-exclusion chromatography. The purified protein exhibited a molecular mass of approximately 46 kDa by polyacrylamide gel electrophoresis and 40,875 Da, for the apoprotein, using mass spectrometry which also confirmed the presence of both heme and FAD prosthetic groups. The fusion protein showed immunological cross-reactivity with both anti-rat cytochrome b(5) and anti-rat cytochrome b(5) reductase antibodies indicating the conservation of antigenic determinants from both native domains. Spectroscopic analysis indicated the fusion protein contained both a b-type cytochrome and flavin chromophors with properties identical to those of the native proteins. Amino-terminal and internal amino acid sequencing confirmed the identity of peptides derived from both the heme- and flavin-binding domains with sequences identical to the deduced amino acid sequence. The isolated fusion protein retained NADH:ferricyanide reductase activity (k(cat) = 8.00 x 10(2) s(-1), K(NADH)(m) = 4 microM, K(FeCN(6))(m) = 11 microM) comparable to that of that of native NADH:cytochrome b(5) reductase and also exhibited both NADH:cytochrome c reductase activity (k(cat) = 2.17 x 10(2) s(-1), K(NADH)(m) = 2 microM, K(FeCN(6))(m) = 11 microM, K(Cyt.c)(m) = 1 microM) and NADH:methemoglobin reductase activity (k(cat) = 4.40 x 10(-1) s(-1), K(NADH)(m) = 3 microM, K(mHb)(m) = 47 microM), the latter two activities indicating efficient electron transfer from FAD to heme and retention of physiological function. This work represents the first successful bacterial expression of a soluble, catalytically competent, rat hepatic cytochrome b(5)-cytochrome b(5) reductase fusion protein that retains the functional properties characteristic of the individual heme and flavin domain.     

Immunological similarity between NADH-cytochrome b5 reductase of erythrocytes and liver microsomes.

In a number of animal species soluble NADH-cytochrome b5 reductase of erythrocytes was compared with membrane-bound NADH-cytochrome b5 reductase of liver microsomes by using an antibody to purified NADH-cytochrome b5 reductase from rat liver microsomes. The results obtained indicated clearly that they are immunologically very similar to each other. The data with erythrocyte ghosts suggested that cytochrome b5 and NADH-cytochrome b5 reductase are also present in the ghost.     

Purification and characterization of a soluble form of rat liver NADPH-cytochrome P-450 reductase highly expressed in Escherichia coli

A recombinant cDNA of rat liver NADPH-cytochrome P-450 reductase (CPR), which lacks the N-terminal hydrophobic region, was amplified by PCR and cloned. The N-truncated cDNA named tCPR was ligated into a pBAce vector and expressed. The tCPR protein expressed in Escherichia coli was recovered into the soluble fraction of the cell lysate and purified to homogeneity by three sequential purification procedures; (I) anion-exchange chromatography on a DEAE-cellulose (DE-52) column, (II) affinity chromatography on 2('),5(')-ADP Sepharose 4B, and (III) chromatography on a hydroxyapatite column. The average yield was 47mg per liter of culture medium. The absorption spectrum of the purified tCPR protein was identical to that of a native full-length CPR purified from rat liver, indicating that tCPR also possesses one molecule each of FAD and FMN. The tCPR protein was able to reduce cytochrome c and was also able to assist heme degradation by a soluble form of rat heme oxygenase-1. However, it failed to support the O-deethylation of 7-ethoxycoumarin by cytochrome P-450 1A1, indicating that the presence of the N-terminal hydrophobic domain is necessary for CPR to interact with cytochrome P-450. Previously, to prepare a soluble form of CPR, full-length CPR was treated with proteinases that selectively removed the N-terminal domain. With the expression system established in this study, however, the soluble and biologically active tCPR protein can be readily prepared in large amounts. This expression system will be useful for mechanistic as well as structural studies of CPR.     

Rapid identification of medically important yeasts by electrophoretic protein patterns

A simple electrophoretic method for yeast identification was evaluated. Whole cells were extracted by SDS and the protein profiles obtained in SDS-PAGE after Coomassie blue staining were compared for 52 strains from 9 species of yeast or yeast-like fungi commonly isolated from man (Candida albicans, C. glabrata, C. guilliermondii, C. krusei, C. parapsilosis, C. pseudotropicalis, C. tropicalis, Geotrichum candidum, Saccharomyces cerevisiae). The corresponding patterns showed 30 to 45 polypeptides in the range 95-20 kDa and were clearly different for the 9 species. No differences could be detected between strains from the same species. The characteristic patterns were obtained within 24 h allowing rapid identification of the most commonly encountered clinical yeast isolates.