Association between the occurrence of buccally displaced canine and palatal and craniofacial morphology in adolescents.

The main objective of the present research study is to evaluate the association between the occurrence of buccally displaced canine (BDC) and the palatal as well as the craniofacial morphology in adolescents in accordance at the early permanent dentition. As the experimental group, 100 adolescents of Chinese ethnicity (mean age 13.05 years) with crowding and buccally displaced canine (BDC-c) were selected in comparison with the same number of candidates (mean age 12.59 years) without BDC and crowding as control group. Digital dental casts and cephalograms were collected for three dimensional (3D) and cephalometric measurements. An independent sample T-test was used to compare the cephalometric values between the two groups. Logistic regression as commonly statistical methods used in empirical study including categorical dependent variables was used to identify the joint effects of the dental variables' 3D measurements. When comparing the groups with above analysis, patients with BDC showed a statistically significant narrower and higher palatal vault. For the cephalometric variables, the anterior cranial base length, sagittal position of the maxilla (SNA), sagittal position of the mandible (SNB), and skeletal relationship between maxilla and mandible (ANB) appeared to be smaller, whilst palatal plane angle (SN-PP), Frankfort-mandibular plane angle (FMA), anterior facial height, and lower facial height were larger in BDC-c control group (p < 0.05). A smaller inter-first premolar width was significant in the prediction model (p = 0.002). This study highlights that BDC-c participants in early permanent dentition exhibited a narrower dental arch and higher palatal vault, of which a smaller inter-first premolar width would significantly increase the occurrence of BDC.

Structures of Helicobacter pylori uridylate kinase: insight into release of the product UDP.

Uridylate kinase (UMPK; EC 2.7.4.22) transfers the γ-phosphate of ATP to UMP, forming UDP. It is allosterically regulated by GTP. Structures of Helicobacter pylori UMPK (HpUMPK) complexed with GTP (HpUMPK-GTP) and with UDP (HpUMPK-UDP) were determined at 1.8 and 2.5 Šresolution, respectively. As expected, HpUMPK-GTP forms a hexamer with six GTP molecules at its centre. Interactions between HpUMPK and GTP are made by the ß3 strand of the sheet, loop ß3α4 and the α4 helix. In HpUMPK-UDP, the hexameric symmetry typical of UMPKs is absent. Only four of the HpUMPK molecules bind UDP; the other two HpUMPK molecules are in the UDP-free state. The asymmetric hexamer of HpUMPK-UDP, which has an exposed dimer interface, may assist in UDP release. Furthermore, the flexibility of the α2 helix, which interacts with UDP, is found to increase when UDP is absent in HpUMPK-UDP. In HpUMPK-GTP, the α2 helix is too flexible to be observed. This suggests that GTP binding may affect the conformation of the α2 helix, thereby promoting UDP release.

Crystal structure of a membrane-embedded H+-translocating pyrophosphatase.

H(+)-translocating pyrophosphatases (H(+)-PPases) are active proton transporters that establish a proton gradient across the endomembrane by means of pyrophosphate (PP(i)) hydrolysis. H(+)-PPases are found primarily as homodimers in the vacuolar membrane of plants and the plasma membrane of several protozoa and prokaryotes. The three-dimensional structure and detailed mechanisms underlying the enzymatic and proton translocation reactions of H(+)-PPases are unclear. Here we report the crystal structure of a Vigna radiata H(+)-PPase (VrH(+)-PPase) in complex with a non-hydrolysable substrate analogue, imidodiphosphate (IDP), at 2.35 Å resolution. Each VrH(+)-PPase subunit consists of an integral membrane domain formed by 16 transmembrane helices. IDP is bound in the cytosolic region of each subunit and trapped by numerous charged residues and five Mg(2+) ions. A previously undescribed proton translocation pathway is formed by six core transmembrane helices. Proton pumping can be initialized by PP(i) hydrolysis, and H(+) is then transported into the vacuolar lumen through a pathway consisting of Arg 242, Asp 294, Lys 742 and Glu 301. We propose a working model of the mechanism for the coupling between proton pumping and PP(i) hydrolysis by H(+)-PPases.