Chloride promotes refolding of active Vibrio alkaline phosphatase through an inactive dimeric intermediate with an altered interface

Publisher's version (útgefin grein)Most enzymes are homodimers or higher order multimers. Cold‐active alkaline phosphatase from Vibrio splendidus (VAP) transitions into a dimer with very low activity under mild denaturation conditions. The desire to understand why this dimer fails to efficiently catalyse phosphomonoester hydrolysis led us to investigate interfacial communication between subunits. Here, we studied in detail the unfolding mechanism at two pH values and in the presence or absence of sodium chloride. At pH 8.0, the denaturation model had to include an inactive dimer intermediate and follow the pathway: N2 → I2 → 2U. At pH 10.5, the model was of a two‐state nature. Enzyme activity was not recovered under several examined refolding conditions. However, in the presence of 0.5 m NaCl, the enzyme was nearly fully reactivated after urea treatment. Thermal inactivation experiments were biphasic where the inactivation could be detected using CD spectroscopy at 190–200 nm. By incorporating a bimane fluorescence probe at the dimer interface, we could monitor inactivation/denaturation at two distinct sites at the dimer interface. A change in bimane fluorescence at both sites was observed during inactivation, but prior to the global unfolding event. Furthermore, the rate of change in bimane fluorescence correlated with inactivation rates at 40 °C. These results indicate and support the hypothesis that the subunits of VAP are only functional in the dimeric state due to the cooperative nature of the reaction mechanism when proper crosstalk between subunits is facilitated.Icelandic Research Fund. Grant Number: 141619‐051Peer reviewe

Cold-active alkaline phosphatase is irreversibly transformed into an inactive dimer by low urea concentrations

Post-print (lokagerð höfundar)Alkaline phosphatase is a homodimeric metallo-hydrolase where both Zn2+ and Mg2+ are important for catalysis and stability. Cold-adapted alkaline phosphatase variants have high activity at low temperatures and lower thermal stability compared with variants from mesophilic hosts. The instability, and thus inactivation, could be due to loose association of the dimers and/or loosely bound Mg2+ in the active site, but this has not been studied in detail for the cold-adapted variants. Here, we focus on using the intrinsic fluorescence of Trp in alkaline phosphatase from the marine bacterium Vibrio splendidus (VAP) to probe for dimerization. Trp → Phe substitutions showed that two out of the five native Trp residues contributed mostly to the fluorescence emission. One residue, 15 Å away from the active site (W460) and highly solvent excluded, was phosphorescent and had a distant role in substrate binding. An additional Trp residue was introduced to the dimer interface to act as a possible probe for dimerization. Urea denaturation curves indicated that an inactive dimer intermediate, structurally equivalent to the native state, was formed before dimer dissociation took place. This is the first example of the transition of a native dimer to an inactive dimer intermediate for alkaline phosphatase without using mutagenesis, ligands, or competitive inhibition.Financial support from the Icelandic Research Fund (project 141619-051) and the Science Institute of the University of Iceland is gratefully acknowledged. The authors also extend their gratitude to Tinna Pálmadóttir for performing the experiment of Fig. 2B.Peer reviewe

Structural phylogeny by profile extraction and multiple superimposition using electrostatic congruence as a discriminator

Phylogenetic analysis of proteins using multiple sequence alignment (MSA) assumes an underlying evolutionary relationship in these proteins which occasionally remains undetected due to considerable sequence divergence. Structural alignment programs have been developed to unravel such fuzzy relationships. However, none of these structure based methods have used electrostatic properties to discriminate between spatially equivalent residues. We present a methodology for MSA of a set of related proteins with known structures using electrostatic properties as an additional discriminator (STEEP). STEEP first extracts a profile, then generates a multiple structural superimposition providing a consolidated spatial framework for comparing residues and finally emits the MSA. Residues that are aligned differently by including or excluding electrostatic properties can be targeted by directed evolution experiments to transform the enzymatic properties of one protein into another. We have compared STEEP results to those obtained from a MSA program (ClustalW) and a structural alignment method (MUSTANG) for chymotrypsin serine proteases. Subsequently, we used PhyML to generate phylogenetic trees for the serine and metallo-β-lactamase superfamilies from the STEEP generated MSA, and corroborated the accepted relationships in these superfamilies. We have observed that STEEP acts as a functional classifier when electrostatic congruence is used as a discriminator, and thus identifies potential targets for directed evolution experiments. In summary, STEEP is unique among phylogenetic methods for its ability to use electrostatic congruence to specify mutations that might be the source of the functional divergence in a protein family. Based on our results, we also hypothesize that the active site and its close vicinity contains enough information to infer the correct phylogeny for related proteins

pH-Dependent Binding of Chloride to a Marine Alkaline Phosphatase Affects the Catalysis, Active Site Stability, and Dimer Equilibrium

Post-print (lokagerð höfundar)The effect of ionic strength on enzyme activity and stability varies considerably between enzymes. Ionic strength is known to affect the catalytic activity of some alkaline phosphatases (APs), such as Escherichia coli AP, but how ions affect APs is debated. Here, we studied the effect of various ions on a cold-adapted AP from Vibrio splendidus (VAP). Previously, we have found that the active form of VAP is extremely unstable at low ionic strengths. Here we show that NaCl increased the activity and stability of VAP and that the effect was pH-dependent in the range of pH 7–10. The activity profile as a function of pH formed two maxima, indicating a possible conformational change. Bringing the pH from the neutral to the alkaline range was accompanied by a large increase in both the Ki for inorganic phosphate (product inhibition) and the KM for p-nitrophenyl phosphate. The activity transitions observed as the pH was varied correlated with structural changes as monitored by tryptophan fluorescence. Thermal and urea-induced inactivation was shown to be accompanied by neither dissociation of the active site metal ions nor dimer dissociation. This would suggest that the inactivation involved subtle changes in active site conformation. Furthermore, the VAP dimer equilibrium was studied for the first time and shown to highly favor dimerization, which was dependent on pH and NaCl concentration. Taken together, the data support a model in which anions bind to some specific acceptor in the active site of VAP, resulting in great stabilization and catalytic rate enhancement, presumably through a different mechanism.Icelandic Research Fund 141619Peer reviewe

The dipeptidyl peptidase IV inhibitors vildagliptin and K-579 inhibit a phospholipase C: a case of promiscuous scaffolds in proteins.

The long term side effects of any newly introduced drug is a subject of intense research, and often raging controversies. One such example is the dipeptidyl peptidase-IV (DPP4) inhibitor used for treating type 2 diabetes, which is inconclusively implicated in increased susceptibility to acute pancreatitis. Previously, based on a computational analysis of the spatial and electrostatic properties of active site residues, we have demonstrated that phosphoinositide-specific phospholipase C (PI-PLC) from Bacillus cereus is a prolyl peptidase using in vivo experiments. In the current work, we first report the inhibition of the native activity of PI-PLC by two DPP4 inhibitors - vildagliptin (LAF-237) and K-579. While vildagliptin inhibited PI-PLC at micromolar concentrations, K-579 was a potent inhibitor even at nanomolar concentrations. Subsequently, we queried a comprehensive, non-redundant set of 5000 human proteins (50% similarity cutoff) with known structures using serine protease (SPASE) motifs derived from trypsin and DPP4. A pancreatic lipase and a gastric lipase are among the proteins that are identified as proteins having promiscuous SPASE scaffolds that could interact with DPP4 inhibitors. The presence of such scaffolds in human lipases is expected since they share the same catalytic mechanism with PI-PLC. However our methodology also detects other proteins, often with a completely different enzymatic mechanism, that have significantly congruent domains with the SPASE motifs. The reported elevated levels of serum lipase, although contested, could be rationalized by inhibition of lipases reported here. In an effort to further our understanding of the spatial and electrostatic basis of DPP4 inhibitors, we have also done a comprehensive analysis of all 76 known DPP4 structures liganded to inhibitors till date. Also, the methodology presented here can be easily adopted for other drugs, and provide the first line of filtering in the identification of pathways that might be inadvertently affected due to promiscuous scaffolds in proteins

The dipeptidyl peptidase IV inhibitors vildagliptin and K-579 inhibit a phospholipase C: a case of promiscuous scaffolds in proteins

The long term side effects of any newly introduced drug is a subject of intense research, and often raging controversies. One such example is the dipeptidyl peptidase-IV (DPP4) inhibitor used for treating type 2 diabetes, which is inconclusively implicated in increased susceptibility to acute pancreatitis. Previously, based on a computational analysis of the spatial and electrostatic properties of active site residues, we have demonstrated that phosphoinositide-specific phospholipase C (PI-PLC) from Bacillus cereus is a prolyl peptidase using in vivo experiments. In the current work, we first report the inhibition of the native activity of PI-PLC by two DPP4 inhibitors - vildagliptin (LAF-237) and K-579. While vildagliptin inhibited PI-PLC at micromolar concentrations, K-579 was a potent inhibitor even at nanomolar concentrations. Subsequently, we queried a comprehensive, non-redundant set of 5000 human proteins (50% similarity cutoff) with known structures using serine protease (SPASE) motifs derived from trypsin and DPP4. A pancreatic lipase and a gastric lipase are among the proteins that are identified as proteins having promiscuous SPASE scaffolds that could interact with DPP4 inhibitors. The presence of such scaffolds in human lipases is expected since they share the same catalytic mechanism with PI-PLC. However our methodology also detects other proteins, often with a completely different enzymatic mechanism, that have significantly congruent domains with the SPASE motifs. The reported elevated levels of serum lipase, although contested, could be rationalized by inhibition of lipases reported here. In an effort to further our understanding of the spatial and electrostatic basis of DPP4 inhibitors, we have also done a comprehensive analysis of all 76 known DPP4 structures liganded to inhibitors till date. Also, the methodology presented here can be easily adopted for other drugs, and provide the first line of filtering in the identification of pathways that might be inadvertently affected due to promiscuous scaffolds in proteins

The dipeptidyl peptidase IV inhibitors vildagliptin and K-579 inhibit a phospholipase C: a case of promiscuous scaffolds in proteins [version 3; peer review: 2 approved]

Publisher's version (útgefin grein)The long term side effects of any newly introduced drug is a subject of intense research, and often raging controversies. One such example is the dipeptidyl peptidase-IV (DPP4) inhibitor used for treating type 2 diabetes, which is inconclusively implicated in increased susceptibility to acute pancreatitis. Previously, based on a computational analysis of the spatial and electrostatic properties of active site residues, we have demonstrated that phosphoinositide-specific phospholipase C (PI-PLC) from Bacillus cereus is a prolyl peptidase using in vivo experiments. In the current work, we first report the inhibition of the native activity of PI-PLC by two DPP4 inhibitors - vildagliptin (LAF-237) and K-579. While vildagliptin inhibited PI-PLC at micromolar concentrations, K-579 was a potent inhibitor even at nanomolar concentrations. Subsequently, we queried a comprehensive, non-redundant set of 5000 human proteins (50% similarity cutoff) with known structures using serine protease (SPASE) motifs derived from trypsin and DPP4. A pancreatic lipase and a gastric lipase are among the proteins that are identified as proteins having promiscuous SPASE scaffolds that could interact with DPP4 inhibitors. The presence of such scaffolds in human lipases is expected since they share the same catalytic mechanism with PI-PLC. However our methodology also detects other proteins, often with a completely different enzymatic mechanism, that have significantly congruent domains with the SPASE motifs. The reported elevated levels of serum lipase, although contested, could be rationalized by inhibition of lipases reported here. In an effort to further our understanding of the spatial and electrostatic basis of DPP4 inhibitors, we have also done a comprehensive analysis of all 76 known DPP4 structures liganded to inhibitors till date. Also, the methodology presented here can be easily adopted for other drugs, and provide the first line of filtering in the identification of pathways that might be inadvertently affected due to promiscuous scaffolds in proteins.FMG thanks the Spanish Ministerio de Ciencia e Innovacion for grant No. BFU 2012-36241, and the University of the Basque Country for grant No. IT 849-13. BJ and RV acknowledge financial support from Tata Institute of Fundamental Research (Department of Atomic Energy). Additionally, BJR is thankful to the Department of Science and Technology for the JC Bose Award Grant. BA extends gratitude to the University of Iceland Research Found for supporting the project financially (grant No. 141619). AMD wishes to acknowledge grant #12-0130-SA from California Department of Food and Agriculture CDFA PD/GWSS Board. MO was supported in part by a Grant-in-aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan; (grant No. 21790431). The work in Liege was supported by an IUAP program funded by the Belgian federal government.Peer reviewe

Promiscuous scaffolds in proteins - non-native, non-additive and non-trivial

Publisher's version (útgefin grein)Promiscuity, the ability of an enzyme to catalyze diverse activities using the same active site, sets up the stage for the evolution of complex organisms through gene duplication and specialization. The detection of promiscuous motifs is crucial to understand the physiological relevance of a protein, or for any endeavor that intends to rationally modify these latent capabilities to design new proteins under laboratory conditions. We have established a methodology for identifying catalytic residues based on spatial and electrostatic congruence with known active site configurations. Here, we discuss insights gained in several initiatives using our method on different enzymes.Icelandic reasearch fund (RANNÍS) No. 141619Peer reviewe

Þú þarft að geta tekið þessar beygjur og sveigjur

Miklar tækniframfarir hafa átt sér stað á síðastliðnum árum og eru þær þegar farnar að hafa áhrif á vinnumarkaðinn og samfélagið í heild sinni. Lítið hefur verið skrifað á íslensku um fjórðu iðnbyltinguna og áhrif hennar á vinnumarkaðinn. Megin markmið rannsóknarinnar var að skoða hver áhrif fjórðu iðnbyltingarinnar verða á vinnumarkað og samfélagið á Íslandi í náinni framtíð. Tekið var mið af sögu fyrri iðnbyltinga, fræðigreina sem skrifaðar hafa verið um fjórðu iðnbyltinguna erlendis og hérlendis og það svo tengt við niðurstöður rannsóknarinnar. Framkvæmd var eigindleg rannsókn þar sem tekin voru viðtöl við fimm einstaklinga á vinnumarkaðnum með fjölbreyttan bakgrunn. Niðurstöður rannsóknarinnar leiddu í ljós að töluverðar breytingar hafa orðið á störfum fólks og að tækniframfarir munu að öllum líkindu hafa mikil áhrif á störf í framtíðinni. Grundvallarbreyting hefur orðið á viðhorfi stjórnenda til starfsmanna. Einnig þurfa starfshættir og menntun í samfélaginu að aðlagast eða breytast. Búast má við töluverðum samfélagsbreytingum í kjölfar fjórðu iðnbyltingarinnar og mikilvægt að huga strax að því hvernig hindra megi að auðurinn safnist enn frekar á hendur fárra og að fátækt aukist í heiminum. Áhugavert er að sjá hversu fjölbreytt svör viðmælenda voru. Viðmælendur komu víða við í vangaveltum um hvernig samfélagið verði í framtíðinni og komu viðmælendur meðal annars inn á mikilvægi þess að innviðir væru tilbúnir fyrir iðnbyltinguna