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G Woldegiorgis

Publications and source records attributed to G Woldegiorgis.

At least 19 recordsLinked to original sources
PubMed2001

Pig liver carnitine palmitoyltransferase I, with low Km for carnitine and high sensitivity to malonyl-CoA inhibition, is a natural chimera of rat liver and muscle enzymes.

The outer mitochondrial membrane enzyme carnitine palmitoyltransferase I (CPTI) catalyzes the initial and regulatory step in the beta-oxidation of fatty acids. The genes for the two isoforms of CPTI-liver (L-CPTI) and muscle (M-CPTI) have been cloned and expressed, and the genes encode for enzymes with very different kinetic properties and sensitivity to malonyl-CoA inhibition. Pig L-CPTI encodes for a 772 amino acid protein that shares 86 and 62% identity, respectively, with rat L- and M-CPTI. When expressed in Pichia pastoris, the pig L-CPTI enzyme shows kinetic characteristics (carnitine, K(m) = 126 microM; palmitoyl-CoA, K(m) = 35 microM) similar to human or rat L-CPTI. However, the pig enzyme, unlike the rat liver enzyme, shows a much higher sensitivity to malonyl-CoA inhibition (IC(50) = 141 nM) that is characteristic of human or rat M-CPTI enzymes. Therefore, pig L-CPTI behaves like a natural chimera of the L- and M-CPTI isotypes, which makes it a useful model to study the structure--function relationships of the CPTI enzymes.

Amino Acid Sequence↗
PubMed2000

Identification by mutagenesis of conserved arginine and tryptophan residues in rat liver carnitine palmitoyltransferase I important for catalytic activity.

Carnitine palmitoyltransferase I catalyzes the conversion of long-chain acyl-CoA to acylcarnitines in the presence of l-carnitine. To determine the role of the conserved arginine and tryptophan residues on catalytic activity in the liver isoform of carnitine palmitoyltransferase I (L-CPTI), we separately mutated five conserved arginines and two tryptophans to alanine. Substitution of arginine residues 388, 451, and 606 with alanine resulted in loss of 88, 82, and 93% of L-CPTI activity, respectively. Mutants R601A and R655A showed less than 2% of the wild type L-CPTI activity. A change of tryptophan 391 and 452 to alanine resulted in 50 and 93% loss in carnitine palmitoyltransferase activity, respectively. The mutations caused decreases in catalytic efficiency of 80-98%. The residual activity in the mutant L-CPTIs was sensitive to malonyl-CoA inhibition. Mutants R388A, R451A, R606A, W391A, and W452A had no effect on the K(m) values for carnitine or palmitoyl-CoA. However, these mutations decreased the V(max) values for both substrates by 10-40-fold, suggesting that the main effect of the mutations was to decrease the stability of the enzyme-substrate complex. We suggest that conserved arginine and tryptophan residues in L-CPTI contribute to the stabilization of the enzyme-substrate complex by charge neutralization and hydrophobic interactions. The predicted secondary structure of the 100-amino acid residue region of L-CPTI, containing arginines 388 and 451 and tryptophans 391 and 452, consists of four alpha-helices similar to the known three-dimensional structure of the acyl-CoA-binding protein. We predict that this 100-amino acid residue region constitutes the putative palmitoyl-CoA-binding site in L-CPTI.

Amino Acid Sequence↗
PubMed2000

The subcellular localization of acetyl-CoA carboxylase 2.

Animals, including humans, express two isoforms of acetyl-CoA carboxylase (EC ), ACC1 (M(r) = 265 kDa) and ACC2 (M(r) = 280 kDa). The predicted amino acid sequence of ACC2 contains an additional 136 aa relative to ACC1, 114 of which constitute the unique N-terminal sequence of ACC2. The hydropathic profiles of the two ACC isoforms generally are comparable, except for the unique N-terminal sequence in ACC2. The sequence of amino acid residues 1-20 of ACC2 is highly hydrophobic, suggesting that it is a leader sequence that targets ACC2 for insertion into membranes. The subcellular localization of ACC2 in mammalian cells was determined by performing immunofluorescence microscopic analysis using affinity-purified anti-ACC2-specific antibodies and transient expression of the green fluorescent protein fused to the C terminus of the N-terminal sequences of ACC1 and ACC2. These analyses demonstrated that ACC1 is a cytosolic protein and that ACC2 was associated with the mitochondria, a finding that was confirmed further by the immunocolocalization of a known human mitochondria-specific protein and the carnitine palmitoyltransferase 1. Based on analyses of the fusion proteins of ACC-green fluorescent protein, we concluded that the N-terminal sequences of ACC2 are responsible for mitochondrial targeting of ACC2. The association of ACC2 with the mitochondria is consistent with the hypothesis that ACC2 is involved in the regulation of mitochondrial fatty acid oxidation through the inhibition of carnitine palmitoyltransferase 1 by its product malonyl-CoA.

Acetyl-CoA Carboxylase↗
PubMed2000

The first 28 N-terminal amino acid residues of human heart muscle carnitine palmitoyltransferase I are essential for malonyl CoA sensitivity and high-affinity binding.

Heart/skeletal muscle carnitine palmitoyltransferase I (M-CPTI) is 30-100-fold more sensitive to malonyl CoA inhibition than the liver isoform (L-CPTI). To determine the role of the N-terminal region of human heart M-CPTI on malonyl CoA sensitivity and binding, a series of deletion mutations were constructed ranging in size from 18 to 83 N-terminal residues. All of the deletions except Delta83 were active. Mitochondria from the yeast strains expressing Delta28 and Delta39 exhibited a 2.5-fold higher activity compared to the wild type, but were insensitive to malonyl CoA inhibition and had complete loss of high-affinity malonyl CoA binding. The high-affinity site (K(D1), B(max1)) for binding of malonyl CoA to M-CPTI was completely abolished in the Delta28, Delta39, Delta51, and Delta72 mutants, suggesting that the decrease in malonyl CoA sensitivity observed in these mutants was due to the loss of the high-affinity binding entity of the enzyme. Delta18 showed only a 4-fold loss in malonyl CoA sensitivity but had activity and high-affinity malonyl CoA binding similar to the wild type. Replacement of the N-terminal domain of L-CPTI with the N-terminal domain of M-CPTI does not change the malonyl CoA sensitivity of the chimeric L-CPTI, suggesting that the amino acid residues responsible for the differing sensitivity to malonyl CoA are not located in this N-terminal region. These results demonstrate that the N-terminal residues critical for activity and malonyl CoA sensitivity in M-CPTI are different from those of L-CPTI.

Amino Acid Sequence↗
PubMed2000

Functional characterization of mammalian mitochondrial carnitine palmitoyltransferases I and II expressed in the yeast Pichia pastoris.

Mitochondrial carnitine palmitoyltransferases I and II (CPTI and CPTII), together with the carnitine carrier, transport long-chain fatty acyl-CoA from the cytosol to the mitochondrial matrix for beta-oxidation. Recent progress in the expression of CPTI and CPTII cDNA clones in Pichia pastoris, a yeast with no endogenous CPT activity, has greatly facilitated the characterization of these important enzymes in fatty acid oxidation. It is now well established that yeast-expressed CPTI is a catalytically active, malonyl CoA-sensitive, distinct enzyme that is reversibly inactivated by detergents. CPTII is a catalytically active, malonyl CoA-insensitive, distinct enzyme that is detergent stable. Reconstitution studies with yeast-expressed CPTI have established for the first time that detergent inactivation of CPTI is reversible, suggesting that CPTI is active only in a membrane environment. By constructing a series of deletion mutants of the N-terminus of liver CPTI, we have mapped the residues essential for malonyl CoA inhibition and binding to the conserved first six N-terminal amino acid residues. Mutation of glutamic acid 3 to alanine abolished malonyl CoA inhibition and high affinity malonyl CoA binding, but not catalytic activity, whereas mutation of histidine 5 to alanine caused partial loss in malonyl CoA inhibition. Our mutagenesis studies demonstrate that glutamic acid 3 and histidine 5 are necessary for malonyl CoA inhibition and binding to liver CPTI, but not catalytic activity.

Amino Acid Sequence↗
PubMed1999

A single amino acid change (substitution of glutamate 3 with alanine) in the N-terminal region of rat liver carnitine palmitoyltransferase I abolishes malonyl-CoA inhibition and high affinity binding.

We have recently shown by deletion mutation analysis that the conserved first 18 N-terminal amino acid residues of rat liver carnitine palmitoyltransferase I (L-CPTI) are essential for malonyl-CoA inhibition and binding (Shi, J., Zhu, H., Arvidson, D. N. , Cregg, J. M., and Woldegiorgis, G. (1998) Biochemistry 37, 11033-11038). To identify specific residue(s) involved in malonyl-CoA binding and inhibition of L-CPTI, we constructed two more deletion mutants, Delta12 and Delta6, and three substitution mutations within the conserved first six amino acid residues. Mutant L-CPTI, lacking either the first six N-terminal amino acid residues or with a change of glutamic acid 3 to alanine, was expressed at steady-state levels similar to wild type and had near wild type catalytic activity. However, malonyl-CoA inhibition of these mutant enzymes was reduced 100-fold, and high affinity malonyl-CoA binding was lost. A mutant L-CPTI with a change of histidine 5 to alanine caused only partial loss of malonyl-CoA inhibition, whereas a mutant L-CPTI with a change of glutamine 6 to alanine had wild type properties. These results demonstrate that glutamic acid 3 and histidine 5 are necessary for malonyl-CoA binding and inhibition of L-CPTI by malonyl-CoA but are not required for catalysis.

Alanine↗
PubMed1998

Deletion of the conserved first 18 N-terminal amino acid residues in rat liver carnitine palmitoyltransferase I abolishes malonyl-CoA sensitivity and binding.

To assess the role of the 130 N-terminal amino acid residues of rat liver carnitine palmitoyltransferase I (L-CPTI) on malonyl-CoA sensitivity and binding, we constructed a series of mutants with deletions of the 18, 35, 52, 73, 83, or 129 most N-terminal amino acid residues. The deletion mutants were expressed in the yeast Pichia pastoris. We determined the effects of these mutations on L-CPTI activity, malonyl-CoA sensitivity, and binding in isolated mitochondria prepared from the yeast strains expressing the wild-type and deletion mutants. The mutant protein that lacked the first 18 N-terminal amino acid residues, Delta18, had activity and kinetic properties similar to wild-type L-CPTI, but it was almost completely insensitive to malonyl-CoA inhibition (I50 = 380 microM versus 2.0 microM). In addition, loss of malonyl-CoA sensitivity in Delta18 was accompanied by a 70-fold decrease in affinity for malonyl CoA (KD = 70 nM versus 1.1 nM) compared to wild-type L-CPTI. Deletion of the first 35, 52, 73, and 83 N-terminal amino acid residues had a similar effect on malonyl-CoA sensitivity as did the 18-residue deletion mutant, and there was a progressive reduction in the affinity for malonyl-CoA binding. By contrast, deletion of the first 129 N-terminal amino acid residues resulted in the synthesis of an inactive protein. To our knowledge, this is the first report to demonstrate a critical role for these perfectly conserved first 18 N-terminal amino acid residues of L-CPTI in malonyl-CoA sensitivity and binding.

Amino Acid Sequence↗
PubMed1997

Functional studies of yeast-expressed human heart muscle carnitine palmitoyltransferase I.

Long-chain fatty acids are the primary source of energy production in the heart. Carnitine palmitoyltransferase I (CPT-I) catalyzes the first reaction in the transport of long-chain fatty acids from the cytoplasm to the mitochondrion, a rate-limiting step in beta-oxidation. In this study, we report the functional expression of the human heart/skeletal muscle isoform of CPT-I (M-CPT-I) in the yeast Pichia pastoris. Screening of a human heart cDNA library with cDNA fragments encoding the rat heart M-CPT-I resulted in the isolation of a single full-length human heart M-CPT-I cDNA clone. The clone has an open reading frame of 2316 bp with a 5' untranslated region of 38 bp and a 256-bp 3' untranslated region with the poly(A)+ addition sequence AATAAA. The predicted protein has 772 amino acids and a molecular mass of 88 kDa. Northern blot analysis of mRNAs from different human tissues using the human M-CPT-I cDNA as a probe revealed an abundant transcript of approximately 3.1 kb that was only present in human heart and skeletal muscle tissue. Expression of the human M-CPT-I cDNA in P. pastoris, a yeast with no endogenous CPT activity, produced an 80-kDa protein that was located in the mitochondria. Isolated mitochondria from the M-CPT-I expression strain exhibited a malonyl-coenzyme A (CoA)-sensitive CPT activity that was detergent labile. The I50 for malonyl-CoA inhibition of the yeast-expressed M-CPT-I was 69 nM, and the Kms for carnitine and palmitoyl-CoA were 666 and 42 microM, respectively. The I50 for malonyl-CoA inhibition of the heart enzyme is 30 times lower than that of the yeast-expressed liver CPT-I, and the Km for carnitine is more than 20 times higher than that of the liver CPT-I. This is the first report of the expression of a heart CPT-I in a system devoid of endogenous CPT activity and the functional characterization of a human heart M-CPT-I in the absence of the liver isoform and CPT-II.

Amino Acid Sequence↗
PubMed1997

Reconstitution of highly expressed human heart muscle carnitine palmitoyltransferase I.

The human heart muscle carnitine palmitoyltransferase I (M-CPTI) gene was expressed at high levels from a strain of the methylotrophic yeast Pichia pastoris containing approximately 24 copies of the expression vector. Levels of M-CPTI were more than ten-fold higher than previously reported by our group with a single-copy strain (Arch. Biochem. Biophys., in press) and were sufficient to perform reconstitution studies on the membrane protein, a key step in purification and structural analysis of the enzyme. Solubilization of yeast mitochondria containing M-CPTI in 5% Triton X-100 abolished M-CPTI activity. The detergent-inactivated M-CPTI was then reconstituted by removal of the detergent in the presence of phospholipids. The reconstituted proteoliposomes exhibited M-CPTI activity of 2.4 nmol palmitoylcarnitine formed/mg protein/min, a recovery of 23% of the activity present in the starting mitochondrial preparation. The malonyl-CoA sensitivity of the reconstituted reactivated M-CPTI was 88%. This is the first demonstration of direct reactivation of malonyl-CoA-sensitive M-CPTI activity from solubilized materials from any organism. Previously, M-CPTI was presumed to be irreversibly inactivated by detergents.

Alcohol Oxidoreductases↗
PubMed1997

Functional characterization of mitochondrial carnitine palmitoyltransferases I and II expressed in the yeast Pichia pastoris.

The rate-limiting step in beta oxidation is the conversion of long-chain acyl-CoA to acylcarnitine, a reaction catalyzed by the outer mitochondrial membrane enzyme carnitine palmitoyltransferase I (CPTI) and inhibited by malonyl-CoA. The acylcarnitine is then translocated across the inner mitochondrial membrane by the carnitine/acylcarnitine translocase and converted back to acyl-CoA by CPTII. Although CPTII has been examined in detail, studies on CPTI have been hampered by an inability to purify CPTI in an active form from CPTII. In particular, it has not been conclusively demonstrated that CPTI is even catalytically active, or whether sensitivity of CPTI to malonyl-CoA is an intrinsic property of the enzyme or is contained in a separate regulatory subunit that interacts with CPTI. To address these questions, the genes for CPTI and CPTII were separately expressed in Pichia pastoris, a yeast with no endogenous CPT activity. High levels of CPT activity were present in purified mitochondrial preparations from both CPTI- and CPTII-expressing strains. Furthermore, CPTI activity was highly sensitive to inhibition by malonyl-CoA while CPTII was not. Thus, CPT catalytic activity and malonyl-CoA sensitivity are contained within a single CPTI polypeptide in mammalian mitochondrial membranes. We describe the kinetic characteristics for the yeast-expressed CPTs, the first such report for a CPTI enzyme in the absence of CPTII. Yeast-expressed CPTI is inactivated by detergent solubilization. However, removal of the detergent in the presence of phospholipids resulted in the recovery of malonyl-CoA-sensitive CPTI activity, suggesting that CPTI requires a membranous environment. CPTI is thus reversibly inactivated by detergents.

Acyl Coenzyme A↗
PubMed1995

Photoaffinity labeling of mitochondrial proteins with 2-azido [32P]palmitoyl CoA.

A long-chain fatty acyl CoA photolabel, 2-azido [32P]palmitoyl CoA, was synthesized and its covalent interaction with mitochondrial membrane proteins examined. On binding of 2-azido [32P]palmitoyl CoA to beef heart mitochondria, two polypeptides were primarily labeled, the 30 kDa ADP/ATP carrier and a 41 kDa protein of unknown identity. Carboxyatractyloside and palmitoyl CoA completely protected against labeling of the 30 kDa protein indicating that it was the ADP/ATP carrier. With inverted submitochondrial particles, only the 30 kDa polypeptide was labeled by 2-azido [32P]palmitoyl CoA. The labeling was inhibited by bongkrekic acid and palmitoyl CoA but not carboxyatractyloside, providing evidence that the ADP/ATP carrier was covalently bound from the matrix side of the membrane. In brown adipose tissue mitochondria, 2-azido [32P]palmitoyl CoA photolabeled the ADP/ATP carrier and the 32 kDa uncoupling protein with some minor labeling of 36 and 68 kDa polypeptides. The results indicated that this physiological photolabeling reagent with the azido group on the CoA portion of the molecule interacts like 2-azido ADP with nucleotide binding sites of a number of important enzymes in cell metabolism. Moreover, the evidence strongly supports the hypothesis that long chain fatty acyl CoA esters are natural ligands for key nucleotide binding proteins.

Acyl Coenzyme A↗
PubMed1994

A single mutation in uncoupling protein of rat brown adipose tissue mitochondria abolishes GDP sensitivity of H+ transport.

The uncoupling protein is one of a family of mitochondrial transport proteins involved in energy metabolism. It dissipates oxidative energy to generate heat, either by catalyzing proton transport directly or by catalyzing fatty acid anion transport, thus enabling fatty acids to act as cycling protonophores. This transport process is tightly regulated by purine nucleotides. We have expressed uncoupling protein in yeast and examined its proton transport activity after its reconstitution into proteoliposomes. A directed change of Arg276 to Leu or Gln completely abolished nucleotide inhibition of protonophoretic action of the reconstituted mutant uncoupling proteins without affecting the transport process. Arg276 is the first residue of functional importance to be identified in uncoupling protein. Mutation of the homologous residue in the yeast ADP/ATP translocator prevented the growth of yeast on a nonfermentable carbon source, presumably by interfering with nucleotide exchange (Nelson, D. R., Lawson, J. E., Klingenberg, M., and Douglas, M. G. (1993) J. Mol. Biol. 230, 1159-1170). Demonstration of the essential role of a single homologous residue in protein-nucleotide interaction within these two transporters is the first direct evidence that uncoupling protein and the ADP/ATP translocator belong to the same gene family.

Adipose Tissue, Brown↗
PubMed1993

Myocardial metabolism in chronic reperfusion after nontransmural infarction in pig hearts.

The purpose of these studies was to evaluate metabolic behavior in a 4-day reperfusion model in pigs after induction of subendocardial infarction. Two groups of swine [sham and intervention (Int) groups, n = 7) and 10 hearts per group, respectively] were prepared comparably with two surgical procedures separated over 4 days. In the Int group at the time of the first surgery, coronary flow in the left anterior descending (LAD) circulation was partially restricted (by 60%) for 60 min and was then reperfused. LAD myocardium at the time of the second surgery in both groups was extracorporeally perfused aerobically (5.9 +/- 0.2 ml.min-1.g dry wt-1) for 60 min and infused by equilibrium labeling with [U-14C]-palmitate and [5-3H]glucose to estimate fatty acid oxidation and exogenous glucose utilization. During extracorporeal perfusion, regional myocardial shortening and oxygen consumption were comparable between groups despite a marginal impairment in ATP resynthesis by mitochondria (26% decrease, P < 0.071) in Int hearts and a significant decline in mitochondrial respiration (45% decrease in respiratory control rate, P < 0.008; and 41% decrease in state 3 respiration, P < 0.032) as compared with sham hearts. Fatty acid oxidation described by 14CO2 production was 34.00 +/- 4.72 mumol.h-1.g dry wt-1 (averaged from 30-60 min of perfusion) in sham hearts but was decreased (by 48%, P < 0.004) in Int hearts. This reduction in fatty acid utilization may in part be explained by declines in the observed activity of the mitochondrial membrane transporter enzyme, carnitine palmitoyltransferase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Reconstitution and partial purification of the glibenclamide-sensitive, ATP-dependent K+ channel from rat liver and beef heart mitochondria.

The transport properties of mitochondria are such that net potassium flux across the inner membrane determines mitochondrial volume. It has been known that K+ uptake is mediated by diffusive leak driven by the high electrical membrane potential maintained by redox-driven, electrogenic proton ejection and that regulated K+ efflux is mediated by an 82-kDa inner membrane K+/H+ antiporter. There is also long-standing suggestive evidence for the existence of an inner membrane protein designed to catalyze electrophoretic K+ uptake into mitochondria. We report reconstitution of a highly purified inner membrane protein fraction from rat liver and beef heart mitochondria that catalyzes electrophoretic K+ flux in liposomes and channel activity in planar lipid bilayers. The unit conductance of the channel at saturating [K+] is about 30 pS. Reconstituted K+ flux is inhibited with high affinity by ATP and ADP in the presence of divalent cations and by glibenclamide in the absence of divalent cations. The mitochondrial ATP-dependent K+ channel is selective for K+, with a Km of 32 mM, and does not transport Na+. K+ transport depends on voltage in a manner consistent with a channel activity that is not voltage-regulated. Thus, the mitochondrial ATP-dependent K+ channel exhibits properties that are remarkably similar to those of the ATP-dependent K+ channels of plasma membranes.

Adenosine Diphosphate↗
PubMed1992

Conferral of malonyl coenzyme A sensitivity to purified rat heart mitochondrial carnitine palmitoyltransferase.

An immunoaffinity column against the 86-kDa malonyl-CoA-binding protein of beef heart mitochondria was prepared, and the properties of the eluates were compared to those of eluates of an anti-carnitine palmitoyltransferase immunoaffinity column. Both eluates contain seven to eight major proteins with a malonyl-CoA-binding capacity of approximately 5 nmol/mg of protein; in contrast, the eluates from a preimmune IgG column did not contain any of the major proteins. The eluates from both immunoaffinity columns conferred malonyl-CoA sensitivity to purified rat heart mitochondrial carnitine palmitoyltransferase (CPTi/CPT-II). Addition of phospholipids increased the degree of malonyl-CoA inhibition. Doubling the amount of column eluate approximately doubled the malonyl-CoA sensitivity when added to a fixed amount of CPT; i.e., the inhibition increased from 32 to 67%. These results show that CPTi/CPT-II is capable of exhibiting malonyl-CoA sensitivity in the presence of malonyl-CoA-binding proteins. The results do not support the concept that the 86-kDa malonyl-CoA-binding protein is detergent-inactivated carnitine palmitoyltransferase I;rather, they suggest that it is a regulatory subunit of a carnitine palmitoyltransferase complex.

Animals↗
PubMed1992

Restoration of malonyl-CoA sensitivity of soluble rat liver mitochondria carnitine palmitoyltransferase by reconstitution with a partially purified malonyl-CoA binding protein.

Solubilization of rat liver mitochondria in 5% Triton X-100 followed by chromatography on a hydroxylapatite column resulted in the identification of malonyl-CoA binding protein(s) distinct from a major carnitine palmitoyltransferase activity peak. Further purification of the malonyl-CoA binding protein(s) on an acyl-CoA affinity column followed by sodium dodecyl sulfate gel electrophoresis indicated proteins with Mr mass of 90 and 45-33 kDa. A purified liver malonyl-CoA binding fraction, which was devoid of carnitine palmitoyltransferase, and a soluble malonyl-CoA-insensitive carnitine palmitoyltransferase were reconstituted by dialysis in a liposome system. The enzyme activity in the reconstituted system was decreased by 50% in the presence of 100 microM malonyl-CoA. Rat liver mitochondria carnitine palmitoyltransferase may be composed of an easily dissociable catalytic unit and a malonyl-CoA sensitivity conferring regulatory component.

Animals↗
PubMed1990

Characterization of a low molecular weight protein of the ATP synthetase complex from beef heart and rat liver mitochondria with a high affinity monoclonal antibody.

A monoclonal antibody raised against beef heart mitochondria elicited a strong reaction on Western Blot with a 16 kD protein in preparations of beef heart mitochondria, ammonia particles, oligomycin sensitive ATPase and Complex V, in addition to showing a lesser affinity for the partially purified 30 kD ADP/ATP carrier. The antibody also reacted with a 17 kD protein in rat liver mitochondria and an enriched membrane vesicle fraction. The N-terminal sequence of the first twenty amino acids of both the beef heart and rat liver proteins contained significant homology. Comparison with results in the literature indicate that the proteins represent the delta subunit of the ATP synthetase complex. Further evidence suggests that the epitope for the antibody may reside at the C-terminal 30-40 amino acid residues of both proteins.

Amino Acid Sequence↗