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Crystallization and preliminary diffraction data for adenosylcobalamin-dependent methylmalonyl-CoA mutase from Propionibacterium shermanii.

Pink crystals of methylmalonyl-CoA mutase from Propionibacterium shermanii, a coenzyme B12 (5'-deoxyadenosylcobalamin)-dependent enzyme, have been obtained by the hanging-drop method in two different forms. One form lies in the space group P21, with unit cell dimensions a = 122 A, b = 160 A and c = 90 A, with beta = 104 degrees (1 A = 0.1 nm). There are two alpha beta dimers in the asymmetric unit. The crystals diffract to 3.2 A resolution and are suitable for high resolution X-ray diffraction studies.

Crystallization↗

Crystallization and preliminary X-ray diffraction studies of the human erythrocyte bisphosphoglycerate mutase.

Bisphosphoglycerate mutase (EC 2.7.5.4) catalyzes the synthesis and breakdown of 2,3-diphosphoglycerate in red cells. The human enzyme, cloned and expressed in Escherichia coli has been crystallized in the rhombohedral space group R32 with a = b = c = 100.4 A and alpha = beta = gamma = 81.2 degrees. The asymmetric unit contains either a dimeric enzyme molecule, or a monomer.

Bisphosphoglycerate Mutase↗

Plasma phosphoglycerate mutase as a marker of muscular dystrophy.

An elevation of phosphoglycerate mutase (PMG) has been detected in the blood plasma of the genetically dystrophic chicken and in Duchenne muscular dystrophy (DMD) patients. In the dystrophic chicken, plasma PGM in the pectoral muscle was simultaneously depressed to less than one-half that of the normal chicken. In a group of 9 DMD patients, plasma PGM activity was found to be significantly raised above the normal range. A survey of a small group of plasma specimens from human fetuses at risk for muscular dystrophy also suggested that PGM merits investigation as a potential adjunct to other diagnostic indices.

Animals↗

Differential expression of creatine kinase and phosphoglycerate mutase isozymes during development in aneural and innervated human muscle culture.

Several enzymes that occur in multimolecular forms undergo transitions during myogenesis. Studies of such developmentally regulated isozymes (e.g. creatine kinase) indicate that muscle cells, cultured in the absence of neural tissue never develop fully mature isozyme patterns, but continue to express large amounts of 'housekeeping' isozymes that are characteristically present in fetal muscle. We studied two developmentally controlled isozymes, creatine kinase (CK) and phosphoglycerate mutase (PGAM) in normal human muscle, both aneurally cultured and co-cultured with fetal mouse spinal cord complex. Innervated cultures attain a greater degree of maturity than non-innervated cultures, as revealed by light and electron microscopy, showing well-developed sarcomeres and motor endplates after several weeks in vitro. During early stages of muscle regeneration in co-culture, characteristic fetal isozyme patterns of CK-BB and PGAM-BB activity predominate, as in aneural cultures. The muscle-specific isozymes (CK-MM; PGAM-MM) begin to appear as the muscle differentiates, and after 2-3 months in co-culture only, virtually all enzyme activity is due to the muscle-specific forms of CK and PGAM, as is normally observed in mature skeletal muscle in vivo.

Animals↗

Purification and characterization of phosphoglycerate mutase isozymes from pig heart.

The three isozymes of phosphoglycerate mutase from pig heart have been purified to homogeneity. The isozymes have a molecular weight of 57000 as determined by gel-filtration chromatography. Discontinuous gel electrophoresis in the presence of sodium dodecyl sulfate yields a single band with a molecular weight of 29000, indicating that the isozymes are dimers composed of subunits of similar mass. Hybridization experiments show that the three isozymes result from homodimeric and heterodimeric combinations of two different subunits. The two types of subunit differ in their heat lability and in the presence of -SH groups essential for enzymatic activity. No remarkable differences exist in the kinetic constants of the purified isozymes. The kinetic pattern is consistent with a 'ping-pong' mechanism. The homogeneous preparations of the three isozymes show intrinsic glycerate-2,3-P2 synthase activity and glycerate-2,3-P2 phosphatase activity which can be stimulated by glycolate-2-P.

Animals↗

Immunological properties of rat phosphoglycerate mutase isozymes.

In mammalian tissues three phosphoglycerate mutase (D-phosphoglycerate 2,3-phosphomutase, EC 5.4.2.1) isozymes result from the homo-dimeric and hetero-dimeric combinations of two subunits (types M and B). Whereas rabbit antisera against type M subunit (purified from rat muscle) and against type BB isozyme (purified from rat brain) possessed a high degree of specificity, both antisera reacted with type BB and MM isozymes, as demonstrated by immunoneutralization and ELISA. Both the M subunit and B subunit were more immunoreactive than their respective dimeric isozymes. Subunits type M and B may possess common antigenic determinants, and some of these determinants may be sterically hindered in their dimeric structures.

Animals↗

Asynchronous regulation of muscle specific isozymes of creatine kinase, glycogen phosphorylase, lactic dehydrogenase and phosphoglycerate mutase in innervated and non-innervated cultured human muscle.

Expression of muscle specific isozymes (MSIs) of creatine kinase (CK, EC 2.7.3.2), glycogen phosphorylase (GP, EC 2.4.1.1), lactate dehydrogenase (LDH, EC 1.1.1.27) and phosphoglycerate mutase (PGAM, EC 2.7.5.3) was studied both in cultured human muscle fibers which had been innervated (InnCHMFs) for 20-83 days, and in their non-innervated (non-InnCHMFs) sister control. In non-InnCHMFs, the MSI of PGAM was never detected, and there was no change in the expression of the MSI of CK during the entire period examined; the expression of MSIs of LDH and GP showed linear increase during the entire period of growth. The expression of MSIs of all 4 enzymes was significantly enhanced in InnCHMFs as compared to non-innervated control. The expression of MSIs of GP and PGAM, and to a lesser degree of LDH increased significantly in correlation with the duration of innervation; the MSI of CK increased linearly only up to 54 days of innervation and plateaued afterward. This study demonstrates: (1) innervation of cultured human muscle fibers by fetal rat spinal cord exerts a time-related maturational influence on their cellular isoenzymatic pattern; (2) to achieve induction and characteristic time-related expression of various MSIs, the requirements for neuronal influences seem to differ.

Bisphosphoglycerate Mutase↗

Purification and properties of the phosphoglycerate mutase isozymes from the mouse.

The two homodimeric isozymes of phosphoglycerate mutase have been purified from murine kidney and muscle. No differences were observed in the Michaelis-Menten constant for the substrate 2-phospho-D-glycerate, in molecular weight, temperature and pH optima, when the purified isozymes were compared. The isozymes differ in their inhibition constants for phosphoenolpyruvate, in their Michaelis constants for 3-phospho-D-glycerate and 2,3-bisphospho-D-glycerate, their thermal and pH lability and in their sensitivity towards mercury ions.

Animals↗

Transcriptional control of yeast phosphoglycerate mutase-encoding gene.

Yeast genes encoding enzymes of the glycolytic pathway are highly expressed due to transcriptional control elements in their promoters. We provide data on such elements in the 5'-noncoding sequences of the Saccharomyces cerevisiae GPM1 gene, encoding phosphoglycerate mutase. Using fusions to the lacZ reporter gene, a detailed deletion analysis was performed. A palindromic sequence was shown to function as an upstream activation site (UAS) and two upstream repressing sites (URS1 and URS2) were located. Western and Northern blot analyses were used to substantiate the data obtained in enzymatic measurements. The regulatory sequences were shown to be functional in the heterologous CYC1 promoter. In addition, a promoter region was detected which mediated general glycolytic control by the GCR1 regulatory factor.

Amino Acid Sequence↗

The gene encoding rat phosphoglycerate mutase subunit M: cloning and promoter analysis in skeletal muscle cells.

The expression of the gene encoding the muscle-specific (M)-subunit of phosphoglycerate mutase (PGAM-M) is restricted to adult skeletal and cardiac muscle. In order to study its expression in muscle, the rat PGAM-M gene has been isolated and sequenced. Rat PGAM-M spans about 2.2 kb and is composed of three exons: 442, 181 and 186-bp long, and two introns of 97 bp and 1.3 bp. The analysis of the 5'-flanking region reveals a promoter which contains multiple DNA regulatory elements and constitutes an ideal model to study muscle gene transcriptional regulation. Thus, the elements responsible for rat PGAM-M muscle-specific expression have been identified by transient transfection in chicken embryo primary cultures, using chimeric constructs of the rat promoter linked to a cat reporter gene. Here, we report that in spite of the abundance of E-box motifs in the rat PGAM-M promoter known for their involvement in muscle gene expression, two DNA elements regulate the muscle-specific transcription of rat PGAM-M: an A/T motif, the putative MEF-2-binding site (myocyte-specific enhancer-binding factor 2), and a proximal 27-bp element which is conserved between the rat and human genes. These two elements define a small promoter (170 bp) sufficient to support potent and skeletal-muscle-specific expression. The conserved 27-bp region contains a transcriptional regulatory element able to confer muscle-specific expression when located upstream from a heterologous TATA box.

Amino Acid Sequence↗

Cloning, expression and sequence analysis of the genes encoding the heterodimeric methylmalonyl-CoA mutase of Porphyromonas gingivalis W50.

Two genes that encode methylmalonyl-CoA mutase (MCM) have been characterised in Porphyromonas gingivalis W50 (Pg). The genes, designated mcmA and mcmB are transcribed in an operon and encode the MCM small subunit (SS, 68,626 Da) and the MCM large subunit (LS, 78,703 Da), respectively. A recombinant Escherichia coli (Ec) clone harbouring the Pg mcmA and mcmB genes expressed MCM activity 280-times higher than that of the Ec control. The C terminus of the MCM LS has sequence homology to domains of a variety of enzymes that consume or produce methylmalonyl-CoA, suggesting that the MCM LS C-terminal domain is involved in substrate binding. The MCM LS C-terminal region also exhibits homology to other enzymes that have cobalamin-containing cofactors. It is likely, therefore, that the C terminus of the MCM LS is an important MCM domain involved in both substrate and cofactor binding.

Amino Acid Sequence↗

Linkage relationships of the human methylmalonyl CoA mutase to the HLA and D6S4 loci on chromosome 6.

The human methylmalonyl CoA mutase (MCM) cDNA has been used to localize the MUT locus on the short arm of chromosome 6 proximal to the glyoxalase locus in 6p deletion cell lines. A HindIII polymorphism identified by the MCM cDNA was used to study linkage relationships of MUT to HLA (A-B-DQ-DR) and D6S4 in the reference CEPH families. The maximum lod score for MUT versus HLA was 3.04 at a recombination fraction of 0.28. The maximum lod score for MUT versus D6S4 was 22.93 at a recombination fraction of 0.01. These data suggest that MUT and D6S4 loci are tightly linked and may be used as one locus in a haplotype form for linkage studies on proximal 6p and diagnostic analysis of pedigrees with mut methylmalonic acidemia.

Cell Line↗

Structure of the human methylmalonyl-CoA mutase (MUT) locus.

The MUT locus encoding the enzyme methylmalonyl-CoA mutase is defective in mut forms of methylmalonic acidemia. This locus has been mapped to chromosome 6p12-21.1. We report cloning and characterization of this locus which comprises 13 exons spanning greater than 35 kb of the genome. The MUT locus exhibits consensus sequences for transcription, splicing, and polyadenylation. The putative promoter region was localized in a CG island 5' to exon I and was shown to direct expression of a beta-galactosidase reporter gene in cultured cells. Of interest is the observation that the first intron occurs within the 5' untranslated region, and no introns separate the mitochondrial targeting sequences and the mature apoenzyme. An informative HindIII polymorphism was localized within the coding sequence and can be assayed using the polymerase chain reaction. These studies describe the structure of the MUTlocus and provide a foundation for characterization of mutations in mut methylmalonic acidemia.

Base Sequence↗

Mapping of the L-methylmalonyl-CoA mutase gene to mouse chromosome 17.

In humans, methylmalonyl acidemia is caused by a deficiency of L-methylmalonyl-CoA mutase (MUT) controlled by a gene that has been mapped to chromosome 6. The mouse homolog of this gene has now been mapped to mouse chromosome 17. Recombinant inbred and congenic strains place the mouse Mut locus 1.06 cM distal to H-2, between Pgk-2 and Ce-2. The relative order of syntenic probes flanking H-2 on mouse chromosome 17 and HLA on human chromosome 6 is shown to be different.

Animals↗

New insight into the catalytic mechanism of chorismate mutases from structural studies.

Chorismate mutase catalyzes the rearrangement of chorismic acid to prephenic acid, which is the first committed step in the biosynthesis of aromatic amino acids. Its catalytic mechanism has been much studied, but is poorly understood. Recent structural information on enzymes from two species, and on an antibody that catalyzes the same reaction, has shed new light on this topic.

Animals↗

Isolation and characterization of another cDNA encoding a chorismate mutase from the phytoparasitic nematode Meloidogyne arenaria.

A new cDNA, named Ma-cm-2, encoding a chorismate mutase (CM), has been isolated from Meloidogyne arenaria. The full-length cDNA, carrying the trans-spliced SL1 leader sequence, was 753-bp long with an open reading frame of 576 bp. The deduced protein MA-CM-2 including amino-terminal signal peptide shows significant similarity to CMs of Meloidogyne incognita, Meloidogyne javanica, and also bacteria. Secondary structure prediction of MA-CM-2 indicates the presence of the three conserved alpha-helix domains present in the Escherichia coli CMs. Reverse transcription and polymerase chain reaction analysis showed that its transcript abundance is high in the early developmental stages and low in later ones. In situ mRNA hybridization revealed that the transcripts of Ma-cm-2 accumulated specifically in the two subventral oesophageal gland cells of M. arenaria. The widespread existence of CMs in the sedentary endoparasitic nematodes implicates that this enzyme plays an important role in the host-parasite interaction.

Amino Acid Sequence↗