4n6v
Partial rotational order disorder structure of human stefin B
Structural highlights
DiseaseCYTB_HUMAN Defects in CSTB are the cause of progressive myoclonic epilepsy type 1 (EPM1) [MIM:254800. EPM1 is an autosomal recessive disorder characterized by severe, stimulus-sensitive myoclonus and tonic-clonic seizures. The onset, occurring between 6 and 13 years of age, is characterized by convulsions. Myoclonus begins 1 to 5 years later. The twitchings occur predominantly in the proximal muscles of the extremities and are bilaterally symmetrical, although asynchronous. At first small, they become late in the clinical course so violent that the victim is thrown to the floor. Mental deterioration and eventually dementia develop.[1] FunctionCYTB_HUMAN This is an intracellular thiol proteinase inhibitor. Tightly binding reversible inhibitor of cathepsins L, H and B. Publication Abstract from PubMedAt present, the determination of crystal structures from data that have been acquired from twinned crystals is routine; however, with the increasing number of crystal structures additional crystal lattice disorders are being discovered. Here, a previously undescribed partial rotational order-disorder that has been observed in crystals of stefin B is described. The diffraction images revealed normal diffraction patterns that result from a regular crystal lattice. The data could be processed in space groups I4 and I422, yet one crystal exhibited a notable rejection rate in the higher symmetry space group. An explanation for this behaviour was found once the crystal structures had been solved and refined and the electron-density maps had been inspected. The lattice of stefin B crystals is composed of five tetramer layers: four well ordered layers which are followed by an additional layer of alternatively placed tetramers. The presence of alternative positions was revealed by the inspection of electron-density score maps. The well ordered layers correspond to the crystal symmetry of space group I422. In addition, the positions of the molecules in the additional layer are related by twofold rotational axes which correspond to space group I422; however, these molecules lie on the twofold axis and can only be related in a statistical manner. When the occupancies of alternate positions and overlapping are equal, the crystal lattice indeed fulfills the criteria of space group I422; when these occupancies are not equal, the lattice only fulfills the criteria of space group I4. Partial rotational lattice order-disorder in stefin B crystals.,Renko M, Taler-Vercic A, Mihelic M, Zerovnik E, Turk D Acta Crystallogr D Biol Crystallogr. 2014 Apr;70(Pt 4):1015-25. doi:, 10.1107/S1399004714000091. Epub 2014 Mar 19. PMID:24699646[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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