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1.
Ekici OD Karla A Paetzel M Lively MO Pei D Dalbey RE 《The Journal of biological chemistry》2007,282(1):417-425
Signal peptidase functions to cleave signal peptides from preproteins at the cell membrane. It has a substrate specificity for small uncharged residues at -1 (P1) and aliphatic residues at the -3 (P3) position. Previously, we have reported that certain alterations of the Ile-144 and Ile-86 residues in Escherichia coli signal peptidase I (SPase) can change the specificity such that signal peptidase is able to cleave pro-OmpA nuclease A in vitro after phenylalanine or asparagine residues at the -1 position (Karla, A., Lively, M. O., Paetzel, M. and Dalbey, R. (2005) J. Biol. Chem. 280, 6731-6741). In this study, screening of a fluorescence resonance energy transfer-based peptide library revealed that the I144A, I144C, and I144C/I86T SPase mutants have a more relaxed substrate specificity at the -3 position, in comparison to the wild-type SPase. The double mutant tolerated arginine, glutamine, and tyrosine residues at the -3 position of the substrate. The altered specificity of the I144C/I86T mutant was confirmed by in vivo processing of pre-beta-lactamase containing non-canonical arginine and glutamine residues at the -3 position. This work establishes Ile-144 and Ile-86 as key P3 substrate specificity determinants for signal peptidase I and demonstrates the power of the fluorescence resonance energy transfer-based peptide library approach in defining the substrate specificity of proteases. 相似文献
2.
Arif?B?Ekici Sevinc?Oezbey Christina?Fuchs Eva?Nelis Christine?Van Broeckhoven Melitta?Schachner Bernd?RautenstraussEmail author 《BMC cell biology》2002,3(1):29
Background
Mutations in P0, the major protein of the myelin sheath in peripheral nerves, cause the inherited peripheral neuropathies Charcot-Marie-Tooth disease type 1B (CMT1B), Dejerine-Sottas syndrome (DSS) and congenital hypomyelination (CH). We reported earlier a de novo insertional mutation c.662_663GC (Ala221fs) in a DSS patient. The c.662_663GC insertion results in a frame shift mutation Ala221fs altering the C-terminal amino acid sequence. The adhesion-relevant intracellular RSTK domain is replaced by a sequence similar to Na+/K+ ATPase. To further clarify the molecular disease mechanisms in this sporadic patient we constructed wild type P0 and the c.662_663GC mutant expression cassettes by site-specific mutagenesis and transfected the constructs into insect cells (S2, High5). To trace the effects in live cells, green fluorescent protein (GFP) has been added to the carboxyterminus of the wild type and mutated P0 protein. 相似文献3.
In this study ultrastructural differences between endothelial cells of different location in Penstemon gentianoides have been examined with electron microscope at mature embryo sac phase. Embryo sac is of the Polygonum type and surrounded by endothelium except the micropylar region. The cuticle is located primarily around the chalazal three-fourths of the embryo sac. Endothelium cells around the chalaza and toward the micropylar region are rich in cytoplasmic organelles. The cytoplasm of endothelial cells near the central cell has large vacuoles and few organelles. There are also plasmodesmas on the anticlinal walls of endothelial cells. The endothelium and the micropylar integumentary cells play a role in transport of metabolites into the embryo sac. 相似文献
4.
During cytochrome c maturation (Ccm), the DsbA-dependent thio-oxidative protein-folding pathway is thought to introduce a disulphide bond into the haem-binding motif of apocytochromes c. This disulphide bond is believed to be reduced through a thio-reductive pathway involving the Ccm components CcdA (DsbD), CcmG and CcmH. Here, we show in Rhodobacter capsulatus that in the absence of DsbA cytochrome c levels were decreased and CcdA or CcmG or the putative glutathione transporter CydDC was not needed for Ccm. This decrease was not due to overproduction of the periplasmic protease DegP as a secondary effect of DsbA absence. In contrast, CcmH was absolutely necessary regardless of DsbA, indicating that compensatory thio-redox interactions excluded it. Remarkably, the double (DsbA-CcmG) and triple (DsbA-CcmG-CcdA) mutants produced cytochromes c at lower levels than the DsbA-null mutants, unless they contained a CcmG derivative (CcmG*) lacking its thio-reductive activity. Purified CcmG* can bind apocytochrome c in vitro, revealing for the first time a thiol-independent, direct interaction between apocytochrome c and CcmG. Furthermore, elimination of the thio-redox components does not abolish cytochrome c production, restricting the number of Ccm components essential for haem-apocyt c ligation per se during Ccm. 相似文献
5.
Astragalus yildirimlii is described and illustrated from Central Anatolia-Turkey. Pollen and seed morphology and chromosome number is given as well. The relationships of the new species are discussed. 相似文献
6.
Georgia Vasileiou Silvia Vergarajauregui Sabine Endele Bernt Popp Christian Büttner Arif B. Ekici Marion Gerard Nuria C. Bramswig Beate Albrecht Jill Clayton-Smith Jenny Morton Susan Tomkins Karen Low Astrid Weber Maren Wenzel Janine Altmüller Yun Li Bernd Wollnik André Reis 《American journal of human genetics》2018,102(3):468-479
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Mutations in the gene encoding the Wnt-signaling component R-spondin 4 (RSPO4) cause autosomal recessive anonychia
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Bergmann C Senderek J Anhuf D Thiel CT Ekici AB Poblete-Gutierrez P van Steensel M Seelow D Nürnberg G Schild HH Nürnberg P Reis A Frank J Zerres K 《American journal of human genetics》2006,79(6):1105-1109
Anonychia is an autosomal recessive disorder characterized by the congenital absence of finger- and toenails. In a large German nonconsanguineous family with four affected and five unaffected siblings with isolated total congenital anonychia, we performed genomewide mapping and showed linkage to 20p13. Analysis of the RSPO4 gene within this interval revealed a frameshift and a nonconservative missense mutation in exon 2 affecting the highly conserved first furin-like cysteine-rich domain. Both mutations were not present among controls and were shown to segregate with the disease phenotype. RSPO4 is a member of the recently described R-spondin family of secreted proteins that play a major role in activating the Wnt/ beta -catenin signaling pathway. Wnt signaling is evolutionarily conserved and plays a pivotal role in embryonic development, growth regulation of multiple tissues, and cancer development. Our findings add to the increasing body of evidence indicating that mesenchymal-epithelial interactions are crucial in nail development and put anonychia on the growing list of congenital malformation syndromes caused by Wnt-signaling-pathway defects. To the best of our knowledge, this is the first gene known to be responsible for an isolated, nonsyndromic nail disorder. 相似文献
9.
Faik Ahmet Karavelioğulları Atilla Ocak Murat Ekici Evren Cabi 《Nordic Journal of Botany》2009,27(3):222-227
Verbascum eskisehirensis Karavel., Ocak & Ekici sp. nov. (sect. Bothrosperma Murb.) is described and illustrated from Turkey. This new species is confined to B3 Eskisehir in central Anatolia. A morphological comparison is made with the closely related species; V. oreophilum K. Koch and V. pyramidatum M. Bieb. In addition, a cluster analysis was conducted and a distribution map of the new species and the related species is also given. 相似文献
10.
Severely incapacitating mutations in patients with extreme short stature identify RNA-processing endoribonuclease RMRP as an essential cell growth regulator
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Thiel CT Horn D Zabel B Ekici AB Salinas K Gebhart E Rüschendorf F Sticht H Spranger J Müller D Zweier C Schmitt ME Reis A Rauch A 《American journal of human genetics》2005,77(5):795-806
The growth of an individual is deeply influenced by the regulation of cell growth and division, both of which also contribute to a wide variety of pathological conditions, including cancer, diabetes, and inflammation. To identify a major regulator of human growth, we performed positional cloning in an autosomal recessive type of profound short stature, anauxetic dysplasia. Homozygosity mapping led to the identification of novel mutations in the RMRP gene, which was previously known to cause two milder types of short stature with susceptibility to cancer, cartilage hair hypoplasia, and metaphyseal dysplasia without hypotrichosis. We show that different RMRP gene mutations lead to decreased cell growth by impairing ribosomal assembly and by altering cyclin-dependent cell cycle regulation. Clinical heterogeneity is explained by a correlation between the level and type of functional impairment in vitro and the severity of short stature or predisposition to cancer. Whereas the cartilage hair hypoplasia founder mutation affects both pathways intermediately, anauxetic dysplasia mutations do not affect B-cyclin messenger RNA (mRNA) levels but do severely incapacitate ribosomal assembly via defective endonucleolytic cleavage. Anauxetic dysplasia mutations thus lead to poor processing of ribosomal RNA while allowing normal mRNA processing and, therefore, genetically separate the different functions of RNase MRP. 相似文献