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PubMedDate not supplied

Inhibition of glucose-6-phosphate phosphohydrolase by 3-mercaptopicolinate and two analogs is metabolically directive.

3-Mercaptopicolinae (3-MP) blocks gluconeogenesis from lactate, pyruvate, alanine, and other substrates through its inhibition of phosphoenolpyruvate carboxykinase. Nevertheless, we observed increased glycogenesis, net glucose uptake, and glucose-6-P levels in livers perfused with glucose in the presence of 3-MP. In perfusions with 20 mM dihydroxyacetone, increased glycogenesis and decreased glucose production were observed with 3-MP. These metabolic effects suggested additional site(s) of action of 3-MP. Further studies showed that 3-MP inhibits glucose-6-P phosphohydrolase activity of intact liver microsomes. Several compounds with structural similarities to 3-MP (2-mercaptonicotinic acid, picolinic acid, cysteine, reduced glutathione, nicotinic acid, quinolinic acid, tryptophan, and pyridine) were tested for their effect on glucose-6-P phosphohydrolase activity. Two of these compounds, 2-mercaptonicotinic acid and picolinic acid, were found to inhibit. In perfusions including 7.5 mM fructose, the addition of 3-MP, 2-mercaptonicotinic acid, or picolinic acid increased glycogenesis, decreased glucose production, and increased hepatic glucose-6-P concentrations. These observations indicate that the inhibition of glucose-6-P phosphohydrolase may play a role in enhanced glycogenesis from glucose, dihydroxyacetone, and fructose in isolated livers from 48-h fasted rats perfused with 3-MP or certain sulfhydryl-containing and sulfhydryl-devoid analogs.

Animals↗
PubMed1990

Increased hepatic mitochondrial capacity in rats with hydroxy-cobalamin[c-lactam]-induced methylmalonic aciduria.

Treatment of rats with the vitamin B12 analogue hydroxy-cobalamin[c-lactam] (HCCL) impairs methylmalonyl-CoA mutase function and leads to methylmalonic aciduria due to intracellular accumulation of propionyl and methylmalonyl-CoA. Since accumulation of these acyl-CoAs disrupts normal cellular regulation, the present investigation characterized metabolism in hepatocytes and liver mitochondria from rats treated subcutaneously with HCCL or saline (control) by osmotic minipump. Consistent with decreased methylmalonyl-CoA mutase activity, 14CO2 production from 1-14C-propionate (1 mM) was decreased by 76% and 82% after 2-3 wk and 5-6 wk of HCCL treatment, respectively. In contrast, after 5-6 wk of HCCL treatment, 14CO2 production from 1-14C-pyruvate (10 mM) and 1-14C-palmitate (0.8 mM) were increased by 45% and 49%, respectively. In isolated liver mitochondria, state 3 oxidation rates were unchanged or decreased, and activities of the mitochondrial enzymes, citrate synthetase, succinate dehydrogenase, carnitine palmitoyltransferase, and glutamate dehydrogenase (expressed per milligram mitochondrial protein) were unaffected by HCCL treatment. In contrast, activities of the same enzymes were significantly increased in both liver homogenate (expressed per gram liver) and isolated hepatocytes (expressed per 10(6) cells) from HCCL-treated rats. The mitochondrial protein per gram liver, calculated on the basis of the recovery of the mitochondrial enzymes, increased by 39% in 5-6 wk HCCL-treated rats. Activities of lactate dehydrogenase, catalase, cyanide-insensitive palmitoyl-CoA oxidation, and arylsulfatase A in liver were not affected by HCCL treatment. Hepatic levels of mitochondrial mRNAs were elevated up to 10-fold in HCCL-treated animals as assessed by Northern blot analysis. Thus, HCCL treatment is associated with enhanced mitochondrial oxidative capacity and an increased mitochondrial protein content per gram liver. Increased mitochondrial oxidative capacity may be a compensatory mechanism in response to the metabolic insult induced by HCCL administration.

Animals↗
PubMed1999

Smoking disturbs mitochondrial respiratory chain function and enhances lipid peroxidation on human circulating lymphocytes.

Mitochondria constitute a source of reactive oxygen species. We tested whether mitochondrial function from human circulating lymphocytes is affected by smoking habit and if this could be associated with an increase in oxidative damage of biological membranes. We prospectively studied 35 smokers and 35 non-smoking healthy individuals matched by age and sex, with a similar physical activity. Individual enzyme activity of complexes II, III and IV of the mitochondrial respiratory chain (MRC) and of glycerol-3-phosphate dehydrogenase activity were measured spectrophotometrically. Intact cell respiration and oxidative rates after addition of pyruvate, succinate and glycerol-3-phosphate were assessed polarographically. Lipid peroxidation of biological membranes was assessed measuring the loss of cis-parinaric acid fluorescence. Results are expressed as means (+/-SD). Smokers showed a significant decrease in complex IV activity compared with non-smokers (112.8 +/- 40.9 versus 146.4 +/- 62.5 nmol/min/mg protein, respectively; 23% of inhibition; P = 0.01), while the rest of the complexes of MRC were unaffected. Conversely, oxidative rate with succinate, but not with the other substrates, was enhanced in smokers compared with non-smokers (16.7 +/- 10.4 versus 11.4 +/- 4.7 nmol oxygen/min/mg protein, respectively; 46% of activation; P = 0. 01). Lipid peroxidation of lymphocyte membranes was increased in smokers with respect to non-smokers (3.49 +/- 1.27 versus 4.39 +/- 1. 76 units of fluorescence/mg protein, respectively; 21% of increase; P = 0.03) and this increase correlated positively with succinate oxidation activation (R = 0.34, P = 0.02) and, to a lesser extent, with complex IV inhibition, although it did not reach statistical significance (R = 0.19, P = 0.18). In smokers, the MRC function of lymphocytes is disturbed and correlates with the degree of oxidative damage of membranes. This mitochondrial dysfunction could contribute to increased endogenous production of reactive oxygen species and could play a role in tobacco carcinogenicity.

Adult↗
PubMed1975

Anthranilate synthetase-anthranilate 5-phosphoribosylpyrophosphate phosphoribosyl-transferase from Salmonella typhimurium. Inactivation of glutamine-dependent anthranilate synthetase by agarose-bound anthranilate.

Exposure of the anthranilate synthetase-anthranilate phosphoribosyltransferase enzyme complex (chorismate pyruvate-lyase (amino-accepting) EC 4.1.3.27 and N-(5-phosphoribosyl)-anthranilate pyrophosphate phosphoribosyl-transferase, EC 2.4.2.18) from Salmonella typhimurium to agarose-bound anthranilate led to the slow inactivation of glutamine-dependent anthranilate synthetase activity, an activity dependent on protein-protein interaction in the enzyme complex. Region I of phosphoribosyltransferase, the location of the enzyme complex glutaminase activity, is the site of alteration. Phosphoribosyltransferase and NH3-dependent anthranilate synthetase activities and trypto phan regulation of phosphoribosyltransferase were unaffected by the anthranilate matrix. The molecular weight (280 000) and subunit molecular weight (62 000) of the enzyme complex eluted from an anthranilate matrix were identical to those of enzyme complex purified by classical methodology. The enzyme complex could be partially protected against inactivation by storiing in 0.1 M L-glutamine or 30% glycerol and completely protected by storing in 50% glycerol at -18 degrees C. Evidence is presented that the anthranilate matrix acts as a hydrophobic matrix and may be binding to and altering a hydrophobic region in the enzyme complex. The anthranilate matrix provides a convenient tool for altering a specific region of an enzyme complex without covalent modification. At the same time, the results demonstrate that affinity matrices are not necessarily innocuous but may subject macromolecules to an adverse environment not previously recognized.

Allosteric Site↗
PubMed2000

High resolution solution structure of the 1.3S subunit of transcarboxylase from Propionibacterium shermanii.

Transcarboxylase (TC) from Propionibacterium shermanii, a biotin-dependent enzyme, catalyzes the transfer of a carboxyl group from methylmalonyl-CoA to pyruvate to form propionyl-CoA and oxalacetate. Within the multi-subunit enzyme complex, the 1.3S subunit functions as the carboxyl group carrier and also binds the other two subunits to assist in the overall assembly of the enzyme. The 1.3S subunit is a 123 amino acid polypeptide (12.6 kDa) to which biotin is covalently attached at Lys 89. The three-dimensional solution structure of the full-length holo-1.3S subunit of TC has been solved by multidimensional heteronuclear NMR spectroscopy. The C-terminal half of the protein (51-123) is folded into a compact all-beta-domain comprising of two four-stranded antiparallel beta-sheets connected by short loops and turns. The fold exhibits a high 2-fold internal symmetry and is similar to that of the biotin carboxyl carrier protein (BCCP) of acetyl-CoA carboxylase, but lacks an extension that has been termed "protruding thumb" in BCCP. The first 50 residues, which have been shown to be involved in intersubunit interactions in the intact enzyme, appear to be disordered in the isolated 1.3S subunit. The molecular surface of the folded domain has two distinct surfaces: one side is highly charged, while the other comprises mainly hydrophobic, highly conserved residues.

Acetyl-CoA Carboxylase↗
PubMed1995

Purification and properties of the lipoate protein ligase of Escherichia coli.

Lipoate is an essential component of the 2-oxoacid dehydrogenase complexes and the glycine-cleavage system of Escherichia coli. It is attached to specific lysine residues in the lipoyl domains of the E2p (lipoate acetyltransferase) subunit of the pyruvate dehydrogenase complex by a Mg(2+)- and ATP-dependent lipoate protein ligase (LPL). LPL was purified from wild-type E. coli, where its abundance is extremely low (< 10 molecules per cell) and from a genetically amplified source. The purified enzyme is a monomeric protein (M(r) 38,000) which forms irregular clusters of needle-like crystals. It is stable at -20 degrees C, but slowly oxidizes to an inactive form containing at least one intramolecular disulphide bond at 4 degrees C. The inactive form could be re-activated by reducing agents or by an as-yet unidentified component (reactivation factor) which is resolved from LPL at the final stage of purification. The pI is 5.80, and the Km values for ATP, Mg2+ and DL-lipoate were determined. Selenolipoate and 6-thio-octanoate were alternative but poorer substrates. Lipoylation was reversibly inhibited by the 6- and 8-seleno-octanoates and 8-thio-octanoate, which reacted with the six cysteine thiol groups of LPL. LPL was inactivated by Cu2+ ions in a process that involved the formation of inter- and intra-molecular disulphide bonds. Studies with lplA mutants lacking LPL activity indicated that E. coli possesses another distinct lipoylation system, although no such activity could be detected in vitro.

Amino Acid Sequence↗
PubMed1998

Oxidative phosphorylation in intact hepatocytes: quantitative characterization of the mechanisms of change in efficiency and cellular consequences.

Two mechanisms may affect the yield of the oxidative phosphorylation pathway in isolated mitochondria: (i) a decrease in the intrinsic coupling of the proton pumps (H+/2e- or H+/ATP), and (ii) an increase in the inner membrane conductance (proton or cation leak). Hence three kinds of modifications can occur and each of them have been characterized in isolated rat liver mitochondria (see preceding chapter by Rigoulet et al.). In intact isolated hepatocytes, these modifications are linked to specific patterns of bioenergetic parameters, i.e. respiratory flux, mitochondrial redox potential, DY, and phosphate potential. (1) The increase in H+/ATP stoichiometry of the mitochondrial ATP synthase, as induced by almitrine [20], leads to a decrease in mitochondrial and cytosolic ATP/ADP ratios without any change in the protonmotive force nor in the respiratory rate or redox potential. (2) In comparison to carbohydrate, octanoate metabolism by beta-oxidation increases the proportion of electrons supplied at the second coupling site of the respiratory chain. This mimics a redox slipping. Octanoate addition results in an increased respiratory rate and mitochondrial NADH/NAD ratio while protonmotive force and phosphate potential are almost unaffected. The respiratory rate increase is associated with a decrease in the overall apparent thermodynamic driving force (2deltaE'o - ndeltap) which confirms the 'redox-slipping-like' effect. (3) An increase in proton conductance as induced by the protonophoric uncoupler 2,4-dinitrophenol (DNP) leads to a decrease, as expected, in the mitochondrial NADH/NAD and ATP/ ADP ratios and in deltapsi while respiratory rate is increased. Thus, each kind of modification (proton leak, respiratory chain redox slipping or increase in H+/ATP stoichiometry of ATPase) is related to a specific set of bioenergetic parameters in intact cells. Moreover, these patterns are in good agreement with the data found in isolated mitochondria. From this work, we conclude that quantitative analysis of four bioenergetic parameters (respiration rate, mitochondrial NADH/ NAD ratio, protonmotive force and mitochondrial phosphate potential) gives adequate tools to investigate the mechanism by which some alterations may affect the yield of the oxidative phosphorylation pathway in intact cells.

2,4-Dinitrophenol↗
PubMed2003

The biotin enzyme family: conserved structural motifs and domain rearrangements.

The biotin carboxylase family is comprised of a group of enzymes that utilize a covalently bound prosthetic group, biotin, as a cofactor. These enzymes, which include acetyl-CoA carboxylase, pyruvate carboxylase, propionyl-CoA carboxylase, methylcrotonyl-CoA carboxylase, geranoyl-CoA carboxylase, oxaloacetate decarboxylase, methylmalonyl-CoA decarboxylase, transcarboxylase and urea amidolyase, are found in diverse biosynthetic pathways in both pro-karyotes and eukaryotes. The reactions catalyzed by most members of this group of enzymes share two common features: (1) carboxylation of biotin, apparently via the formation of a carboxyphosphate intermediate, followed by (2) transcarboxylation of CO(2) from biotin to specific acceptor molecules to yield different products. Structural determinations by NMR and X-ray crystallography, complemented by mutagenesis studies, have identified some motifs that are structurally or catalytically important. Analysis of the amino acid sequences of a number of biotin carboxylases not only shows remarkable similarities within certain domains but also that there appears to have been domain rearrangements between groups of carboxylases. Acyl-coenzyme A derivatives, which bind either as substrates or as allosteric regulators of the biotin carboxylases, do not appear to share any of the CoA binding motifs that have been identified in other CoA-SH/acyl-CoA binding proteins. Further comparisons of biotin-dependent carboxylases with other groups of enzymes in the protein data bank reveal that this family of biotin enzymes has strong similarities in specific domains to a number of ATP-utilizing enzymes and to the lipoyl-containing enzymes. These structural homologies are so extensive as to be highly suggestive of evolutionary relationships between biotin carboxylases and these other enzymes.

Acetyl-CoA Carboxylase↗
PubMed2001

Hepatic oxygen exchange and energy metabolism in hyperdynamic porcine endotoxemia: effects of the combined thromboxane receptor antagonist and synthase inhibitor DTTX30.

OBJECTIVE: We compared the effects of thromboxane receptor antagonist and synthase inhibitor DTTX30 on systemic and liver blood flow, oxygen (O2) exchange and energy metabolism during 24 h of hyperdynamic endotoxemia with untreated endotoxemia. DESIGN: Prospective, randomized, experimental study with repeated measures. SETTING: Investigational animal laboratory. SUBJECTS: Twenty-seven domestic pigs: 16 during endotoxemia with volume resuscitation alone; 11 with endotoxemia, volume resuscitation and treatment with DTTX30. INTERVENTIONS: Continuous infusion of Escherichia coli lipopolysaccharide (LPS) for 24 h together with volume resuscitation. After 12 h of endotoxemia, DTTX30 was administered as a bolus of 0.12 mg kg-1 followed by 12 h continuous infusion of 0.29 mg kg-1 per h. MEASUREMENTS AND RESULTS: DTTX30 effectively counteracted the endotoxin-associated increase in TXB2 levels and increased 6-keto-PGF1 alpha with a significant shift of the thromboxane/prostacyclin ratio towards predominance of prostacyclin. DTTX30 prevented the significant progressive endotoxin-induced decrease of mean arterial pressure (MAP) below baseline while maintaining cardiac output (CO), and increased the fractional contribution of liver blood flow to CO without an effect on either hepatic O2 delivery or O2 uptake. The mean capillary hemoglobin O2 saturation (HbO2) on the liver surface and HbO2 frequency distributions remained unchanged as well. CONCLUSIONS: DTTX30 significantly attenuated the endotoxin-induced derangements of cellular energy metabolism as reflected by the diminished progressive decrease in hepatic lactate uptake rate and a blunted increase in hepatic venous lactate/pyruvate ratios. While endotoxin significantly increased the endogenous glucose production (EGP) rate, EGP returned towards baseline levels in the DTTX30-treated group. Thus, in our model DTTX30 resulted in hemodynamic stabilization concomitant with improved hepatic metabolic performance.

Animals↗
PubMed2005

Lactate racemization as a rescue pathway for supplying D-lactate to the cell wall biosynthesis machinery in Lactobacillus plantarum.

Lactobacillus plantarum is a lactic acid bacterium that produces d- and l-lactate using stereospecific NAD-dependent lactate dehydrogenases (LdhD and LdhL, respectively). However, reduction of glycolytic pyruvate by LdhD is not the only pathway for d-lactate production since a mutant defective in this activity still produces both lactate isomers (T. Ferain, J. N. Hobbs, Jr., J. Richardson, N. Bernard, D. Garmyn, P. Hols, N. E. Allen, and J. Delcour, J. Bacteriol. 178:5431-5437, 1996). Production of d-lactate in this species has been shown to be connected to cell wall biosynthesis through its incorporation as the last residue of the muramoyl-pentadepsipeptide peptidoglycan precursor. This particular feature leads to natural resistance to high concentrations of vancomycin. In the present study, we show that L. plantarum possesses two pathways for d-lactate production: the LdhD enzyme and a lactate racemase, whose expression requires l-lactate. We report the cloning of a six-gene operon, which is involved in lactate racemization activity and is positively regulated by l-lactate. Deletion of this operon in an L. plantarum strain that is devoid of LdhD activity leads to the exclusive production of l-lactate. As a consequence, peptidoglycan biosynthesis is affected, and growth of this mutant is d-lactate dependent. We also show that the growth defect can be partially restored by expression of the d-alanyl-d-alanine-forming Ddl ligase from Lactococcus lactis, or by supplementation with various d-2-hydroxy acids but not d-2-amino acids, leading to variable vancomycin resistance levels. This suggests that L. plantarum is unable to efficiently synthesize peptidoglycan precursors ending in d-alanine and that the cell wall biosynthesis machinery in this species is specifically dedicated to the production of peptidoglycan precursors ending in d-lactate. In this context, the lactate racemase could thus provide the bacterium with a rescue pathway for d-lactate production upon inactivation or inhibition of the LdhD enzyme.

Amino Acids↗
PubMed1997

Absence of observable biotin-protein interactions in the 1.3S subunit of transcarboxylase: an NMR study.

Transcarboxylase (TC) is a biotin-containing enzyme catalyzing the transfer of a carboxyl group from methylmalonyl-CoA to pyruvate to form propionyl-CoA and oxalacetate. The transfer is achieved via carboxylated biotin bound to a 1.3S subunit within the multisubunit enzyme complex. The 1.3S subunit of TC is a 123 amino acid polypeptide, to which biotin is covalently attached at Lys 89. We have overexpressed 1.3S in Escherichia coli and characterized the biotinylated and apo-forms by 1D- and 2D-NMR spectroscopy. To search for protein-biotin interactions, which could modulate the reactivity of the biotin ring on the 1.3S subunit, we have compared the chemical shifts, relaxation parameters, and NH exchange rates of the ureido ring protons of free and 1.3S-bound biotin. These properties are similar for both forms of the biotin. Further, NOE experiments on 1.3S revealed no detectable cross peaks between biotin and the protein. Consistent with these findings, the 2D NMR data for holo- and apo-1.3S are essentially identical indicating little or no changes in conformation between the two forms of the protein. The conclusion that strong protein-biotin interactions do not exist in 1.3S contrasts with the findings for the biotin carboxylase carrier protein from E. coli acetyl-CoA carboxylase, which reveal significant biotin-protein contacts [Athappilly, F. K., and Hendrickson, W. A. (1995) Structure 3, 1407-1419]. Further, the biotin NH1' exchange rates determined for 1.3S show that in the region of optimal activity for TC (pH 5.5-6.5) acid-catalyzed exchange predominates. In this pH range the base-catalyzed rate is too small (< 1 s-1) to account for the turnover rate of the enzyme. Thus, the means by which the N1' atom is activated for nucleophilic attack of the carboxyl group in methylmalonyl-CoA does not appear to depend on interactions within the 1.3S subunit alone; rather activation must occur at the interfaces of the subunits in the holoenzyme.

Acetyl-CoA Carboxylase↗
PubMed1995

Lipoic acid metabolism in Escherichia coli: the lplA and lipB genes define redundant pathways for ligation of lipoyl groups to apoprotein.

Lipoic acid is a covalently bound disulfide-containing cofactor required for function of the pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and glycine cleavage enzyme complexes of Escherichia coli. Recently we described the isolation of the lplA locus, the first gene known to encode a lipoyl-protein ligase for the attachment of lipoyl groups to lipoate-dependent apoenzymes (T. W. Morris, K. E. Reed, and J. E. Cronan, Jr., J. Biol. Chem. 269:16091-16100, 1994). Here, we report an unexpected redundancy between the functions of lplA and lipB, a gene previously identified as a putative lipoate biosynthetic locus. First, analysis of lplA null mutants revealed the existence of a second lipoyl ligase enzyme. We found that lplA null mutants displayed no growth defects unless combined with lipA (lipoate synthesis) or lipB mutations and that overexpression of wild-type LplA suppressed lipB null mutations. Assays of growth, transport, lipoyl-protein content, and apoprotein modification demonstrated that lplA encoded a ligase for the incorporation of exogenously supplied lipoate, whereas lipB was required for function of the second lipoyl ligase, which utilizes lipoyl groups generated via endogenous (lipA-mediated) biosynthesis. The lipB-dependent ligase was further shown to cause the accumulation of aberrantly modified octanoyl-proteins in lipoate-deficient cells. Lipoate uptake assays of strains that overproduced lipoate-accepting apoproteins also demonstrated coupling between transport and the subsequent ligation of lipoate to apoprotein by the LplA enzyme. Although mutations in two genes (fadD and fadL) involved in fatty acid failed to affect lipoate utilization, disruption of the smp gene severely decreased lipoate utilization. DNA sequencing of the previously identified slr1 selenolipoate resistance mutation (K. E. Reed, T. W. Morris, and J. E. Cronan, Jr., Proc. Natl. Acad. Sci. USA 91:3720-3724, 1994) showed this mutation (now called lplA1) to be a G76S substitution in the LplA ligase. When compared with the wild-type allele, the cloned lplA1 allele conferred a threefold increase in the ability to discriminate against the selenium-containing analog. These results support a two-pathway/two-ligase model of lipoate metabolism in E. coli.

Amino Acid Sequence↗
PubMed2002

Characterization of the carboxylate delivery module of transcarboxylase: following spontaneous decarboxylation of the 1.3S-CO2- subunit by NMR and FTIR spectroscopies.

Transcarboxylase (TC) is a multisubunit enzyme that catalyzes the transfer of a carboxylate group from methylmalonyl-CoA (MMCoA) to pyruvate. The CO2- group is shuttled between the MMCoA and pyruvate binding sites by a biotin cofactor, covalently linked to the 1.3S subunit. Fully carboxylated 1.3S can be prepared in vitro using 1.3S, MMCoA, and catalytic amounts of the TC's MMCoA-binding subunit. The 1.3S-CO2- intermediate decarboxylates spontaneously over a period of hours, and this process was characterized by 1D and 2D NMR and FTIR spectroscopies. The NMR data yielded a first-order kinetic constant of 1.4 x 10(-3) min(-1) for the spontaneous decarboxylation. This rate was calculated from the 1D NMR spectrum by measuring the reappearance of biotin's ureido NH protons and the disappearance of peaks at 6.99 and 7.67 ppm assigned to Asn-8 and/or Asn-24 from the 1.3S's N-terminus. The latter peaks are absent in the 1D spectrum of non-carboxylated 1.3S due to exchange between two or more conformations within the N-terminus causing line broadening. It is proposed that interactions between the biotin-CO2- and the N-terminal amino acids perturb this conformational equilibrium causing some N-terminal residues to appear in the 1D NMR spectrum of the carboxylated form. Further details are apparent from a comparison of the 2D spectra of the 1.3S-CO2- and 1.3S proteins, where carboxylation causes several peaks from the C-terminal half to shift as well as the appearance of resonances due to some residues located at the N-terminal half of the protein. FTIR difference spectra were used also to follow spontaneous decarboxylation of the 1.3S-CO2-. For the carboxylated 1.3S, the difference spectra provided the vibrational signature of the CO2- on the biotin ring. A doublet was identified at 1695 and 1699 cm(-1) that increased in intensity with increasing t. This is assigned to an antisymmetric stretching vibration of the CO2- group bound to biotin on the 1.3S protein. Its position and profile provide further evidence for interactions occurring between the biotin-CO2- group and the 1.3S protein. These studies demonstrate the highly mobile, "poised" nature of the 1.3S protein engineered for its role as a CO2- translocator.

Acetyl-CoA Carboxylase↗