Isolation and expression of a rat liver cDNA encoding phosphoglucomutase

Variation in protein abundance profiles in the M. semitendinosus of lambs bred from sires selected on the basis of growth and muscling potential

Relative abundance of proteins localised in the nuclear-enriched, total cell membrane and cytosolic fractions of the semitendinosus muscle was compared between lambs bred from control (C), high muscling (M), and high growth rate (G) sires. In total, 31 proteins were identified whose abundance was differentially regulated between sire type. Differences in hind-limb muscle development between M lambs and C and G lambs were reflected in levels of proteins that regulate or function in cellular mechanisms of protein and energy metabolism. Despite no apparent difference in hind-limb muscle growth in G lambs compared to C, G lambs exhibited marked differences in proteins involved in regulation and function of energy metabolism. These results detail pathways that can be specifically targeted to enhance muscle accretion and growth in lambs. The development of means to manipulate these cellular mechanisms may yield greater gains in muscle accretion and growth rate than breeding on the basis for genetic capacity alone.

A comparative hybridization analysis of yeast DNA with Paramecium parafusin- and different phosphoglucomutase-specific probes

Molecular probes designed for the parafusin (PFUS), the Paramecium exocytic-sensitive phospho glyco protein, gave distinct hybridization patterns in Saccharomyces cerevisiae genomic DNA when compared with different phosphoglucomutase specific probes. These include two probes identical to segments of yeast phosphoglucomutase (PGM) genes 1 and 2. Neither of the PGM probes revealed the 7.4 and 5.9 kb fragments in Bgl II-cut yeast DNA digest detected with the 1.6 kb cloned PFUS cDNA and oligonucleotide constructed to the PFUS region (insertion 3 – I-3) not found in other species. PCR amplification with PFUS-specific primers generated yeast DNA-species of the predicted molecular size which hybridized to the I-3 probe. A search of the yeast genome database produced an unassigned nucleotide sequence that showed 55% identity to parafusin gene and 37% identity to PGM2 (the major isoform of yeast phosphoglucomutase) within the amplified region.Key words: parafusin, phosphoglucomutase, yeast, hybridization, PCR.

Identification of an S100A1/S100B target protein: phosphoglucomutase

Phosphoglucomutase was identified as a potential intracellular S100 target protein because it interacted with two members of the S100 family of calcium-modulated proteins, S100A1 and S100B, in gel overlay experiments. These results were confirmed by affinity chromatography experiments demonstrating that S100A1 and S100B bound to phosphoglucomutase-Sepharose in a calcium-dependent manner. In the reverse experiment, phosphoglucomutase bound to S100A1 and S100B-Sepharose in a calcium-dependent manner. S100A1 inhibited phosphoglucomutase activity in a calcium-dependent manner. In contrast, S100B stimulated phosphoglucomutase activity in a calcium-dependent manner. Other calcium-binding proteins (calmodulin, troponin C, parvalbumin, and alpha-lactalbumin) had no effect on phosphoglucomutase. These results suggest that the effects of S100A1 and S100B are not nonspecific effects of low molecular weight, acidic proteins. This is the first report of an S100 target protein whose activity is antagonistically regulated by S100A1 and S100B, suggesting that cellular diversity in intracellular calcium signaling pathways may be due, at least in part, to the complement of S100 proteins expressed in different cell types.

A novel dystrophin/utrophin-associated protein is an enzymatically inactive member of the phosphoglucomutase superfamily

A 60-kDa protein localised in adherens-type cellular junctions, and previously called aciculin, has been found to interact with the cytoskeletal proteins dystrophin and utrophin [Belkin, A. M. & Burridge, K. (1995) J. Biol. Chem. 270, 6328-6337]. In this study, we report the complete sequence of this protein, and show that it is a novel member of the phosphoglucomutase (PGM) family of proteins. The PGM-related protein (PGM-RP), which contains 506 amino acids (55.6 kDa), is smaller than PGM1 (566 amino acids, 61 kDa). The active site consensus sequences of prokaryotic and eukaryotic mutases are not conserved in PGM-RP, a finding consistent with the lack of enzymatic activity of PGM-RP in vitro, and the absence of a phosphorylated intermediate in vivo. The organisation of the PGM-RP gene is essentially identical to that of PGM1. We propose that the PGM-RP gene, which we have mapped to human chromosome 9qcen-q13, evolved from the PGM1 gene, and encodes a protein with a structural rather than an enzymatic role. PGM-RP is expressed predominantly in muscle with the highest levels in smooth muscle. The significance of the interaction between dystrophin/utrophin and an increasing number of cytoplasmic proteins including PGM-RP remains to be explored.

A 63 kDa phosphoprotein undergoing rapid dephosphorylation during exocytosis in Paramecium cells shares biochemical characteristics with phosphoglucomutase

We have enriched phosphoglucomutase (PGM; EC 5.4.2.2) approximately 20-fold from Paramecium tetraurelia cells by combined fractional precipitation with (NH4)2SO4, gel filtration and anion-exchange chromatography yielding two PGM peaks. Several parameters affecting PGM enzymic activity, molecular mass and pI were determined. Phosphorylation studies were done with isolated endogenous protein kinases. Like the 63 kDa phosphoprotein PP63, which is dephosphorylated within 80 ms during synchronous trichocyst exocytosis [Höhne-Zell, Knoll, Riedel-Gras, Hofer and Plattner (1992) Biochem. J. 286, 843-849], PGM has a molecular mass of 63 kDa and forms of identical pI. Since mammalian PGM activity depends on the presence of glucose 1,6-bisphosphate (Glc-1,6-P2) (which is lost during anion-exchange chromatography), we analysed this aspect with Paramecium PGM. In this case PGM activity was shown not to be lost, due to p-nitrophenyl phosphate-detectable phosphatase(s) (which we have separated from PGM), but also due to loss of Glc-1,6-P2. Like PGM from various vertebrate species, PGM activity from Paramecium can be fully re-established by addition of Glc-1,6-P2 at 10 nM, and it is also stimulated by bivalent cations and insensitive to chelating or thiol reagents. The PGM which we have isolated can be phosphorylated by endogenous cyclic-GMP-dependent protein kinase or by endogenous casein kinase. This results in three phosphorylated bands of identical molecular mass and pI values, as we have shown to occur with PP63 after phosphorylation in vivo (forms with pI 6.05, 5.95, 5.85). In ELISA, antibodies raised against PGM from rabbit skeletal muscle were reactive not only with original PGM but also with PGM fractions from Paramecium. Therefore, PGM and PP63 seem to be identical with regard to widely different parameters, i.e. co-elution by chromatography, molecular mass, phosphorylation by the two protein kinases tested, pI values of isoforms, and immuno-binding. Recent claims that PP63 ('parafusin') would not be identical with PGM specifically in Paramecium are critically evaluated. Since some glycolytic enzymes are discussed as being associated with the Ca(2+)-release channel in muscle sarcoplasmic reticulum, and since sub-plasmalemmal Ca2+ stores in Paramecium closely resemble sarcoplasmic reticulum, a possible function of PP63/PGM in exocytosis regulation is discussed, particularly since dephosphorylation strictly parallels exocytosis.