Bisphosphoglycerate Mutase Deficiency Protects against Cerebral Malaria and Severe Malaria-Induced Anemia.

The replication cycle and pathogenesis of the Plasmodium malarial parasite involves rapid expansion in red blood cells (RBCs), and variants of certain RBC-specific proteins protect against malaria in humans. In RBCs, bisphosphoglycerate mutase (BPGM) acts as a key allosteric regulator of hemoglobin/oxyhemoglobin. We demonstrate here that a loss-of-function mutation in the murine Bpgm (BpgmL166P) gene confers protection against both Plasmodium-induced cerebral malaria and blood-stage malaria. The malaria protection seen in BpgmL166P mutant mice is associated with reduced blood parasitemia levels, milder clinical symptoms, and increased survival. The protective effect of BpgmL166P involves a dual mechanism that enhances the host's stress erythroid response to Plasmodium-driven RBC loss and simultaneously alters the intracellular milieu of the RBCs, including increased oxyhemoglobin and reduced energy metabolism, reducing Plasmodium maturation, and replication. Overall, our study highlights the importance of BPGM as a regulator of hemoglobin/oxyhemoglobin in malaria pathogenesis and suggests a new potential malaria therapeutic target.

Insights into the phosphatase and the synthase activities of human bisphosphoglycerate mutase: a quantum mechanics/molecular mechanics simulation.

Bisphosphoglycerate mutase (BPGM) is a multi-activity enzyme. Its main function is to synthesize the 2,3-bisphosphoglycerate, the allosteric effector of hemoglobin. This enzyme can also catalyze the 2,3-bisphosphoglycerate to the 3-phosphoglycerate. In this study, the reaction mechanisms of both the phosphatase and the synthase activities of human bisphosphoglycerate mutase were theoretically calculated by using the quantum mechanics/molecular mechanics method based on the metadynamics and umbrella sampling simulations. The simulation results not only show the free energy curve of the phosphatase and the synthase reactions, but also reveal the important role of some residues in the active site. Additionally, the energy barriers of the two reactions indicate that the activity of the synthase in human bisphosphoglycerate mutase is much higher than that of the phosphatase. The estimated reaction barriers are consistent with the experimental data. Therefore, our work can give important information to understand the catalytic mechanism of the bisphosphoglycerate mutase family.

Unliganded structure of human bisphosphoglycerate mutase reveals side-chain movements induced by ligand binding.

Erythrocyte-specific bisphosphoglycerate mutase is a trifunctional enzyme which modulates the levels of 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells by virtue of its synthase and phosphatase activities. Low levels of erythrocyte 2,3-BPG increase the affinity of haemoglobin for oxygen, thus limiting the release of oxygen into tissues. 2,3-BPG levels in stored blood decline rapidly owing to the phosphatase activity of bisphosphoglycerate mutase, which is enhanced by a fall in pH. Here, the 1.94 Šresolution X-ray structure of bisphosphoglycerate mutase is presented, focusing on the dynamic nature of key ligand-binding residues and their interaction with the inhibitor citrate. Residues at the binding pocket are complete. In addition, the movement of key residues in the presence and absence of ligand is described and alternative conformations are explored. The conformation in which the ligand citrate would bind at the substrate-binding pocket is proposed, with discussion and representations of its orientation. The characterization of bisphosphoglycerate mutase-citrate interactions will provide a framework for the design of specific inhibitors of the phosphatase activity of this enzyme, which may limit the decline of 2,3-BPG in stored blood.

Seeing the process of histidine phosphorylation in human bisphosphoglycerate mutase.

Bisphosphoglycerate mutase is an erythrocyte-specific enzyme catalyzing a series of intermolecular phosphoryl group transfer reactions. Its main function is to synthesize 2,3-bisphosphoglycerate, the allosteric effector of hemoglobin. In this paper, we directly observed real-time motion of the enzyme active site and the substrate during phosphoryl transfer. A series of high resolution crystal structures of human bisphosphoglycerate mutase co-crystallized with 2,3-bisphosphoglycerate, representing different time points in the phosphoryl transfer reaction, were solved. These structures not only clarify the argument concerning the substrate binding mode for this enzyme family but also depict the entire process of the key histidine phosphorylation as a "slow movie". It was observed that the enzyme conformation continuously changed during the different states of the reaction. These results provide direct evidence for an "in line" phosphoryl transfer mechanism, and the roles of some key residues in the phosphoryl transfer process are identified.

Crystal structure of human bisphosphoglycerate mutase.

Bisphosphoglycerate mutase is a trifunctional enzyme of which the main function is to synthesize 2,3-bisphosphoglycerate, the allosteric effector of hemoglobin. The gene coding for bisphosphoglycerate mutase from the human cDNA library was cloned and expressed in Escherichia coli. The protein crystals were obtained and diffract to 2.5 A and produced the first crystal structure of bisphosphoglycerate mutase. The model was refined to a crystallographic R-factor of 0.200 and R(free) of 0.266 with excellent stereochemistry. The enzyme remains a dimer in the crystal. The overall structure of the enzyme resembles that of the cofactor-dependent phosphoglycerate mutase except the regions of 13-21, 98-117, 127-151, and the C-terminal tail. The conformational changes in the backbone and the side chains of some residues reveal the structural basis for the different activities between phosphoglycerate mutase and bisphosphoglycerate mutase. The bisphosphoglycerate mutase-specific residue Gly-14 may cause the most important conformational changes, which makes the side chain of Glu-13 orient toward the active site. The positions of Glu-13 and Phe-22 prevent 2,3-bisphosphoglycerate from binding in the way proposed previously. In addition, the side chain of Glu-13 would affect the Glu-89 protonation ability responsible for the low mutase activity. Other structural variations, which could be connected with functional differences, are also discussed.

Critical role of human bisphosphoglycerate mutase Cys22 in the phosphatase activator-binding site.

The enzymatic activities catalyzed by bisphosphoglycerate mutase (BPGM, EC 5.4.2.4) have been shown to occur at a unique active site, with distinct binding sites for diphosphoglycerates and monophosphoglycerates. The physiological phosphatase activator (2-phosphoglycolate) binds to BPGM at an undetermined site. BPGM variants were constructed by site-directed mutagenesis of three amino acid residues in the active site to identify residues specifically involved in the binding of the monophosphoglycerates and 2-phosphoglycolate. Substitution of Cys22 by functionally conservative residues, Thr or Ser, caused a great decrease in 2-phosphoglycolate-stimulated phosphatase activity and in the Ka value of the activator, whereas it caused no change in other catalytic activities or in the Km values of 2,3-diphosphoglycerate (2,3-DPG) and glycerate 3-phosphate (3-PG, EC 1.1.1.12), indicating that Cys22 is specifically involved either directly or indirectly in 2-phosphoglycolate binding. Kinetic experiments showed that the Ka of the cofactor and the Km of 3-PG were affected by the substitution of Ser23 indicating that this residue is necessary for the fixation of both 3-PG and 2-phosphoglycolate. The R89K variant has previously been shown to have a modified Km value for monophosphoglycerates, however, its affinity for 2-phosphoglycolate is unaltered, suggesting that Arg89 is specifically involved in monophosphoglycerates binding. CD spectroscopic studies of substrates and cofactor binding showed that 2,3-DPG induced structural modifications of normal and mutated enzymes which could be due to protein phosphorylation. Addition of 2-phosphoglycolate to phosphorylated proteins with normal affinity for the cofactor produced spectra with the same characteristics as unphosphorylated species. In summary, monophosphoglycerates and 2-phosphoglycolate have partially distinct binding sites in human BPGM. The specific implication of the Cys22 residue in 2-phosphoglycolate binding is of great significance in the design of analogs of therapeutic benefit.

Three-dimensional structure of rat acid phosphatase.

The crystal structure of recombinant rat prostatic acid phosphatase was determined to 3 A resolution with protein crystallographic methods. The enzyme subunit is built up of two domains, an alpha/beta domain consisting of a seven-stranded mixed beta-sheet with helices on both sides of the sheet and a smaller alpha domain. Two disulfide bridges between residues 129-340 and 315-319 were found. Electron density at two of the glycosylation sites for parts of the carbohydrate moieties was observed. The dimer of acid phosphatase is formed through two-fold interactions of edge strand 3 from one subunit with strand 3 from the second subunit, thus extending the beta-sheet from seven to 14 strands. Other subunit-subunit interactions involve conserved residues from loops between helices and beta-strands. The fold of the alpha/beta domain is similar to the fold observed in phosphoglycerate mutase. The active site is at the carboxy end of the parallel strands of the alpha/beta domain. There is a strong residual electron density at the phosphate binding site which probably represents a bound chloride ion. Biochemical properties and results from site-directed mutagenesis experiments of acid phosphatase are correlated to the three-dimensional structure.

Improved calculations of compactness and a reevaluation of continuous compact units.

A new method for calculating compactness (Z) that uses look-up table-based algorithms for area and volume computations is introduced. These algorithms can be used in any iterative area or volume calculation, are more than 1000 times faster than the original algorithms, and have equal or better precision. With the faster algorithms it is now possible to calculate the compactness of all continuous units in a protein, and to precisely locate the optimal compact units without the screening functions and limited resolution used previously. These methods have been incorporated into a fully automatic domain finding algorithm, and this method has been applied to the 21 proteins originally analyzed as well as 12 additional proteins. This method is robust, and yields similar units even when applied to coordinates of protein crystals grown under different experimental conditions.

Substitution of His-181 by alanine in yeast phosphoglycerate mutase leads to cofactor-induced dissociation of the tetrameric structure.

The structure and stability of a mutated yeast phosphoglycerate mutase in which His-181 has been replaced by alanine have been studied. The secondary, tertiary and quaternary structures of the mutant enzyme in the absence of ligands are essentially identical to those of the wild-type enzyme as revealed by c.d., fluorescence and cross-linking studies. The mutant enzyme is slightly less stable than the wild-type enzyme towards denaturation by guanidium chloride (GdnHCl). On addition of cofactor 2,3-bisphosphoglycerate, the wild-type enzyme shows increased stability towards GdnHCl. However, addition of cofactor causes dramatic changes in the structure of the mutant enzyme, leading to dissociation of the tetrameric form to dimeric and monomeric species.

Amino acid residues involved in the catalytic site of human erythrocyte bisphosphoglycerate mutase. Functional consequences of substitutions of His10, His187 and Arg89.

Human bisphosphoglycerate mutase (GriP2 mutase) is a trifunctional enzyme which synthesizes and degrades GriP2 in red cells. Among the amino acid residues involved in its active site there are two conserved histidine residues, His10 which is phosphorylated during the catalytic process and His187 for which only speculative data have been made about the potential role during the reactions. Another amino acid residue, Arg89, had not been described as part of this active site but we have recently shown that a natural mutant Arg89-->Cys was highly thermolabile and showed severe perturbations of its enzymatic properties. To understand better the exact role of these residues, replacements of His10 by Gly (H10G) or Asp (H10D), His187 by Asn (H187N), Tyr (H187Y) or Asp (H187D) and Arg89 by Cys (R89C), Ser (R89S), Gly (R89G) or Lys (R89K) were performed by site-directed mutagenesis. The results obtained in this report show that replacement of the His10 residue completely abolished the enzymatic activities. Concerning the His187 residue, our results afford arguments that it plays an essential role in the three catalytic activities. Indeed all these activities are abolished in the two H187Y and H187D variants, whereas they are detectable though strongly diminished, for the H187N variant. In addition mutations at His187 could be distinguishable from those at His10 since the former resulted in a thermolabile enzyme, whereas no significant change in heat stability was observed for the latter. It is noteworthy that the H187N variant is protected against thermal instability by glycerate 2,3-bisphosphate (GriP2). Concerning the Arg89 mutants, R89C, R89S and R89G, the three variants showed characteristics identical to those found in the natural R89C mutant, i.e. loss of 99% of synthase activity, consistent decrease of mutase and 2-phosphoglycolate-stimulated phosphatase activities whereas the unstimulated phosphatase activity was normal. Moreover these mutants were unstable at 55 degrees C but GriP2 was able to protect them against thermal instability. In contrast, the R89K mutant was stable at 55 degrees C. Its synthase and unstimulated phosphatase activities were normal but its mutase and 2-phosphoglycolate-stimulated phosphatase activities were decreased. In addition, Km values for monophosphoglycerates were increased (3.2-fold) in the synthase but normal in mutase activities, whereas Km values for GriP2 were normal in mutase and phosphatase activities.(ABSTRACT TRUNCATED AT 400 WORDS)

Structural modeling of the human erythrocyte bisphosphoglycerate mutase.

Using the crystallographic structure of yeast monophosphoglycerate mutase (MPGM) as a framework we constructed a three-dimensional model of the homologous human erythrocyte bisphosphoglycerate mutase (BPGM). The modeling procedure consisted of substituting 117 amino acid residues and positioning 19 C-terminal residues (unresolved in the X-ray structure) by empirical methods, followed by energy minimization. Among several differences in the active site region the most significant appears to be the replacement of Ser11 in MPGM by Gly in BPGM. The C-terminal segment, which contains mainly basic amino acids, lines the cavity of the active site. The seven amino acid residues, which have been shown to be essential for the three catalytic functions of the human BPGM, interact with the amino acids in the protein core, near the active site. In addition, a cluster of several positively charged residues, particularly arginines, has been identified at the entrance of the active site; this cluster may serve as a secondary binding site for polyanionic substrates or cofactors, as required by a two-binding-site model of the catalytic activities. This model is in agreement with recent studies of an inactive BPGM variant substituent at an Arg position situated in this positively charged cluster. The position of Cys20 in the model constructed suggests that this residue is responsible for inactivation of the enzyme by sulfhydryl reagents. Subunit interfaces have also been constructed for BPGM by analogy with MPGM and suggest that, in addition to the known dimerization of BPGM, tetramerization may occur under certain conditions.

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.