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71.
Intramembrane proteases are important enzymes in biology. The recently solved crystal structures of rhomboid protease GlpG have provided useful insights into the mechanism of these membrane proteins. Besides revealing an internal water-filled cavity that harbored the Ser-His catalytic dyad, the crystal structure identified a novel structural domain (L1 loop) that lies on the side of the transmembrane helices. Here, using site-directed mutagenesis, we confirmed that the L1 loop is partially embedded in the membrane, and showed that alanine substitution of a highly preferred tryptophan (Trp136) at the distal tip of the L1 loop near the lipid:water interface reduced GlpG proteolytic activity. Crystallographic analysis showed that W136A mutation did not modify the structure of the protease. Instead, the polarity for a small and lipid-exposed protein surface at the site of the mutation has changed. The crystal structure, now refined at 1.7 Å resolution, also clearly defined a 20-Å-wide hydrophobic belt around the protease, which likely corresponded to the thickness of the compressed membrane bilayer around the protein. This improved structural model predicts that all critical elements of the catalysis, including the catalytic serine and the L5 cap, need to be positioned within a few angstroms of the membrane surface, and may explain why the protease activity is sensitive to changes in the protein:lipid interaction. Based on these findings, we propose a model where the end of the substrate transmembrane helix first partitions out of the hydrophobic core region of the membrane before it bends into the protease active site for cleavage. 相似文献
72.
Embryogenesis in the reef building corals Acropora intermedia, A. solitaryensis, A. hyacinthus, A. digitifera, and A. tenuis was studied in detail at the morphological level, and the relationships among the animal pole, blastopore, and mouth were investigated for the first time in corals. These species showed essentially the same sequence of development. The embryo undergoes spiral-like holoblastic cleavage despite the presence of a dense isolecithal yolk. After the morula stage, the embryo enters the "prawn-chip" stage, which consists of an irregularly shaped cellular bilayer. The embryo begins to roll inward to form the bowl stage; the round shape observed during this stage suggests that it may be the beginning of gastrulation. However, the blastopore closes and the stomodeum (mouth and pharynx) is formed via invagination at a site near the closed blastopore. During the planula stage, a concavity forms in the aboral region in conjunction with numerous spirocysts, suggesting that spirocysts are used to attach to the substrate before the onset of metamorphosis. 相似文献
73.
We examined gametogenesis and the periodicity of planula release in the brooding coral Acropora (Isopora) brueggemanni (Brook, 1893) on Akajima Island, Okinawa, Japan. We captured the moment when A. brueggemanni would be in the process of self-fertilization. Whole colonies of this species were cultured separately or together with other colonies in plastic containers. We observed no apparent periodicity of planula release in the collected colonies. A few planulae were released intermittently during the observation period, regardless of whether the colonies were cultured individually or with other colonies. Serial paraffin sections of A. brueggemanni showed follicle-like cells surrounding the oocyte during vitellogenesis. In September and October, some spermaries looked half-broken and some ova were surrounded by sperm or spermaries instead of follicle-like cells. Such ova were heart-shaped and may have been cells at the first cleavage stage. These observations suggest that the migration of spermaries and/or oocytes resulted in the close proximity of oocytes and sperm, which would allow self-fertilization. This possibility, together with the production of planula larvae by isolated colonies, suggests that this brooding coral engages in self-fertilization. 相似文献
74.
A pain after thoracotomy may result in a postoperative hypoventilation and lead to atelectases and pneumonia. This study was aimed to compare two analgesic regimens after posterolateral thoracotomy. 80 patients (40-70 years) undergoing thoracotomy were randomized to intercostal catheter analgesia (group A, n = 40) and intercostal nerve block (group B, n = 40). Patients in group A were given 20 mL of 0.5% bupivacaine injections twice a day by intercostal catheter. Intercostal nerve blockade was performed using 5 mL of 0.5% bupivacaine. Intercostal nerve in thoracotomy wound, nerves below and above thoracotomy wound was also injected. PaO2, PaCO2, FVC, FEV1 and visual analog pain scale (VAS) were obtained preoperatively, 24, 48 and 72 hours after operation. Postoperative complications were recorded at the patient discharge. Differences between groups were calculated using Mann-Whitney, KW test and chi square test. The arterial blood gas analyses did not show statistically significant change in any group and time according to the baseline values. FVC and FEV1 decreased significantly in both groups at first postoperative day according to baseline measurements. Patients in B group had significantly higher FEV1 values in the third postoperative day (73.05 +/- 11.25 in A vs. 83.50 +/- 9.17 in B group, p < 0.05). Intercostal catheter analgesia resulted in significantly lower postoperative VAS scores and reduced opioid requirement as compared to intercostal nerve blockade. No differences in the postoperative complications were observed between groups. 相似文献
75.
76.
Escherichia coli GlpG is an orthologue of the rhomboid proteases that catalyse intramembrane proteolysis of specific membrane proteins. We previously showed that it can cleave a type I model membrane protein, Bla-LY2-MBP, having the second transmembrane region of lactose permease (LY2) in vivo and in vitro at the predicted periplasm-membrane boundary region of LY2. Here we investigated the environment of the active site regions of GlpG in the membrane-integrated state by examining the modifiability of Cys residues introduced into the regions around the catalytic residues with membrane-permeable and -impermeable alkylating reagents. The results indicate that the enzyme active site is fully open to the external aqueous phase. GlpG also cleaved a similar fusion protein, Bla-GknTM-MBP, having the transmembrane region of Gurken (GknTM), a physiological substrate of Drosophila rhomboids. Engineered Cys residues in the cleavage site regions of the LY2 and GknTM sequences were efficiently modified with a membrane-impermeable alkylating reagent, showing that these regions are exposed to the periplasm. These results suggest that GlpG cleaves an extramembrane region of substrates, unlike the currently prevailing view that this class of membrane proteases acts against a membrane-embedded polypeptide segment after its lateral entrance into the enzyme's active site. 相似文献
77.
Heidari Reza Farajzadeh Sheikh Ahmad Hashemzadeh Mohammad Farshadzadeh Zahra Salmanzadeh Shokrollah Saki Morteza 《Molecular biology reports》2022,49(5):3811-3822
Molecular Biology Reports - This study was aimed to evaluate the antibiotic resistance, biofilm formation, and genetic diversity of carbapenem-resistant Pseudomonas aeruginosa (CRPA) strains... 相似文献
78.
79.
Matsui K Takaki S Shimada K Hajika M 《Bioscience, biotechnology, and biochemistry》2011,75(6):1174-1176
Oxygenation of lipids during the processing soybeans affects the flavor properties of soy products. We prepared tofu under anaerobic conditions and then evaluated its sensory properties and the compositions of volatiles and oxidized lipids. Anaerobic processing resulted in tofu with less intense richness (kokumi) concomitant with reductions in the amounts of oxidized lipids and volatile compounds. 相似文献
80.