Lipases have a characteristic folding pattern of α/β-hydrolase with mostly parallel β-sheets, flanked on both sides by α-helixes in the structure. The active site is formed by a catalytic triad (serine, aspartic/glutamic acid, and histidine), which is highly conserved. In this study, we have used an integrated experimental and computational approach to identify the extremophilic microbial lipases from the saline habitats of the Thar Desert of Rajasthan. Lipase-producing bacteria were screened and a few samples showed significant lipase activity in both quantitative and qualitative experiments. 16S rRNA sequence analysis of the isolate F1 showed that its sequence is quite similar to that of Bacillus licheniformis and Bacillus haynesii, indicating that this isolate belongs to a new subspecies of Bacillus. The isolate F7 showed maximum sequence identity with Bacillus tequilensis strain 10b. The isolate F7 sequence analysis provided a clear testimony that it can be a new strain of Bacillus tequilensis. The F7 lipase exhibited optimal activity at 60 °C and pH 9. Structural modeling of the F7 lipase revealed that it has a highly conserved alpha/beta hydrolase fold at the sequence and structural level except for the N-terminal region. Interestingly, residue Glu128 was different from the template structure and showed the hydrogen bonding between the side chain of Glu128 and side chains of Asn35 and Gln152 amino acids. Besides, this amino acid also showed salt bridge interaction between Glu128--Lys101. These interactions may be assisting in preserving the stability and activity of lipase at high temperatures and in alkaline pH conditions. The information gathered from this investigation will guide in the rational designing of new more potential extremophilic lipase.

中文翻译：

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从塔尔沙漠盐碱化栖息地分离的一种极端细菌细菌脂肪酶的克隆，鉴定和结构建模。

脂肪酶具有特征性的α/β-水解酶折叠模式，具有大多数平行的β-折叠，在结构的两侧均侧接α-螺旋。活性位点由高度保守的催化三联体（丝氨酸，天冬氨酸/谷氨酸和组氨酸）形成。在这项研究中，我们已经使用了一种综合的实验和计算方法来从拉贾斯坦邦塔尔沙漠的盐碱生境中鉴定出极端微生物的脂肪酶。筛选产生脂肪酶的细菌，在定量和定性实验中，一些样品均显示出明显的脂肪酶活性。分离株F1的16S rRNA序列分析表明其序列与地衣芽孢杆菌和海生芽孢杆菌的序列非常相似，表明该分离株属于芽孢杆菌的新亚种。分离株F7显示了与龙血芽孢杆菌菌株10b的最大序列同一性。分离株F7序列分析提供了明确的证据，证明它可以是新的嗜热芽孢杆菌菌株。F7脂肪酶在60°C和pH 9时表现出最佳活性。F7脂肪酶的结构模型显示，除了N端区域外，它在序列和结构水平上均具有高度保守的α/β水解酶折叠。有趣的是，残基Glu128与模板结构不同，显示出Glu128侧链与Asn35和Gln152氨基酸侧链之间的氢键。此外，该氨基酸还显示出Glu128-Lys101之间的盐桥相互作用。这些相互作用可能有助于在高温和碱性pH条件下保持脂肪酶的稳定性和活性。