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1.  Structural insights into ChpT, an essential dimeric histidine phosphotransferase regulating the cell cycle in Caulobacter crescentus  
The cell-cycle regulator ChpT of C. crescentus is a dimeric histidine phosphotransferase that resembles the typical structure of histidine kinases.
Two-component and phosphorelay signal-transduction proteins are crucial for bacterial cell-cycle regulation in Caulobacter crescentus. ChpT is an essential histidine phosphotransferase that controls the activity of the master cell-cycle regulator CtrA by phosphorylation. Here, the 2.2 Å resolution crystal structure of ChpT is reported. ChpT is a homodimer and adopts the domain architecture of the intracellular part of class I histidine kinases. Each subunit consists of two distinct domains: an N-terminal helical hairpin domain and a C-terminal α/β domain. The two N-terminal domains are adjacent within the dimer, forming a four-helix bundle. The ChpT C-terminal domain adopts an atypical Bergerat ATP-binding fold.
PMCID: PMC3433190  PMID: 22949187
bacterial cell cycle; Caulobacter crescentus; histidine kinases; histidine phosphotransferases
2.  Crystallization and preliminary X-ray diffraction analysis of the peptidylprolyl isomerase Par27 of Bordetella pertussis  
Par27 from B. pertussis, the prototype of a new group of parvulins has been crystallized in two different crystal forms.
Proteins with both peptidylprolyl isomerase (PPIase) and chaperone activities play a crucial role in protein folding in the periplasm of Gram-negative bacteria. Few such proteins have been structurally characterized and to date only the crystal structure of SurA from Escherichia coli has been reported. Par27, the prototype of a new group of parvulins, has recently been identified. Par27 exhibits both chaperone and PPIase activities in vitro and is the first identified parvulin protein that forms dimers in solution. Par27 has been expressed in E. coli. The protein was purified using affinity and gel-filtration chromatographic techniques and crystallized in two different crystal forms. Form A, which belongs to space group P2 (unit-cell parameters a = 42.2, b = 142.8, c = 56.0 Å, β = 95.1°), diffracts to 2.8 Å resolution, while form B, which belongs to space group C222 (unit-cell parameters a = 54.6, b = 214.1, c = 57.8 Å), diffracts to 2.2 Å resolution. Preliminary diffraction data analysis agreed with the presence of one monomer in the asymmetric unit of the orthorhombic crystal form and two in the monoclinic form.
PMCID: PMC2531267  PMID: 18765910
peptidylprolyl isomerases; Par27; parvulins; Bordetella pertussis
3.  Crystallization and preliminary X-ray diffraction studies of the glutaminyl cyclase from Carica papaya latex 
The glutaminyl cyclase isolated from C. papaya latex has been crystallized using the hanging-drop method. Diffraction data have been collected at ESRF beamline BM14 and processed to 1.7 Å resolution.
In living systems, the intramolecular cyclization of N-terminal glutamine residues is accomplished by glutaminyl cyclase enzymes (EC While in mammals these enzymes are involved in the synthesis of hormonal and neurotransmitter peptides, the physiological role played by the corresponding plant enzymes still remains to be unravelled. Papaya glutaminyl cyclase (PQC), a 33 kDa enzyme found in the latex of the tropical tree Carica papaya, displays an exceptional resistance to chemical and thermal denaturation as well as to proteolysis. In order to elucidate its enzymatic mechanism and to gain insights into the structural determinants underlying its remarkable stability, PQC was isolated from papaya latex, purified and crystallized by the hanging-drop vapour-diffusion method. The crystals belong to the orthorhombic space group P212121, with unit-cell parameters a = 62.82, b = 81.23, c = 108.17 Å and two molecules per asymmetric unit. Diffraction data have been collected at ESRF beamline BM14 and processed to a resolution of 1.7 Å.
PMCID: PMC1952388  PMID: 16508091
glutaminyl cyclase

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