The three-dimensional (3D) structure of the hyperthermophilic esterase EstE1 was constructed by homology modeling using Archaeoglobus fulgidus esterase as a reference, and the thermostability-structure relationship was analyzed. Our results verified the predicted 3D structure of EstE1 and identified the ion pair networks and hydrophobic interactions that are critical determinants for the thermostability of EstE1.We previously isolated the hyperthermophilic esterase EstE1 as a new thermophilic esterase belonging to the mammalian hormone-sensitive lipase (HSL) family by functional screening of a metagenomic library constructed with metagenomes from a thermal environment in Indonesia (17). In the HSL family esterase/lipase, three-dimensional (3D) structures have been reported for an esterase from the mesophilic bacterium Alcaligenes eutrophus (2), the brefeldin A esterase (BFAE) from the mesophilic bacterium Bacillus subtilis (20), and two thermostable esterases, EST2 from Alicyclobacillus acido caldarius (5) and AFEST from Archaeoglobus fulgidus (6). These HSL family esterases have equivalent functions, sequence homologies, and similar 3D structures (14). However, they have different thermostabilities. Therefore, comparison of their structures and sequences can help identify crucial factors for the thermostability of proteins. Lacking knowledge of the EstE1 3D structure, we used a combined approach of sequence comparison and molecular modeling to study the thermostability-structure relationship of EstE1.First, we built a 3D model structure of EstE1 (NCBI accession number AY726780) by homology modeling using AFEST as a template, which has a 48.9% amino acid sequence identity to EstE1. The final model structure had 10 ␣-helices and 8 -sheets (Fig. 1). The central -sheet consisted of eight  strands (1 to 8) with a left-handed superhelical twist. The first and last strands cross each other at an angle of about 90°, corresponding to the general canonical ␣/ fold (11, 16). Superposition of the EstE1 model structure with the crystal structure of AFEST (Protein Data Bank [PDB] code 1JJI) resulted in a root-mean-square deviation of 0.5 Å among 1,208 C␣ atoms. The superposition of EstE1 and EST2 structures (PDB code 1EVQ) also displayed a good root-mean-square value of 1.1 Å among 980 C␣ atoms. Secondary-structure-driven sequence alignment, using the ENDscript web server (8), between the predicted secondary structure of the final EstE1 model and the reference protein AFEST as well as EST2 showed that all share a high degree of similarity in both secondary structures and amino acid sequences (Fig. 2).Previously, structural alignments and computer-aided statis- . The hypothetical 3D model was then energy minimized using the Discover program in InsightII. Energy minimization was performed by the method of steepest descents until the energy gradient fell below 1.0 kcal/mol · Å, followed by application of the conjugate gradient minimization method until the energy gradient fell below 0.1 kcal/mol · Å. The model of EstE1 wa...
The pathophysiology, clinical presentation and prognosis of left ventricular obstruction present an important cardiological problem. Various anatomical and functional abnormality can cause this phenomenon. Rarely, left ventricular outflow obstruction can result after mitral valve surgery. We experienced a case of left ventricular outflow obstruction 13 years after mitral valve replacement. The diagnosis was made using two-dimensinal Doppler echocardiography and confirmed by cardiac catheterization. The pressure gradient across the left ventricular outflow obstruction was 96mmHg. A second mitral valve replacement was performed. Because severe fibrosis, pannus around the prosthetic mitral valve and a subaortic web were detected during the operation, the subaortic web was removed. KEY WORDS Mitral valve replacement·Left ventricular outflow obstruction.서 론
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