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首页> 外文期刊>Biochemistry >Intrinsic Structural and Functional Determinants within the Amino Acid Sequence of Mature Pulmonary Surfactant Protein SP-B
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Intrinsic Structural and Functional Determinants within the Amino Acid Sequence of Mature Pulmonary Surfactant Protein SP-B

机译：成熟的肺表面活性剂蛋白SP-B氨基酸序列内的固有结构和功能决定因素。

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摘要

Pulmonary surfactant protein SP-B is absolutely required for proper function of surfactant in the alveoli,and is an important component of therapeutical surfactant preparations used to treat respiratory pathologies.To explore inherent structural and functional determinants within the amino acid sequence of mature SP-B,porcine SP-B has been subjected to extensive disulfide reduction under highly denaturing conditions and to cysteine carboxyamidomethylation,and the structure,lipid-protein interactions,and surface activity of this modified form have been characterized.Refolding of the reduced protein yielded a form (SP-Br) with secondary structure practically identical to that of the native disulfide-linked SP-B dimer.Reduced SP-Br exhibited higher structural flexibility than native SP-B,as indicated by a higher susceptibility of fluorescence emission to quenching by acrylamide and biphasic behavior during interaction of the protein with lipid bilayers and monolayers.SP-Br had,however,effects similar to those of native SP-B on the thermotropic properties of dipalmitoylphosphatidylcholine (DPPC) bilayers.SP-Br was more effective than native SP-B in promoting interfacial adsorption of phospholipid bilayers into interfacial films,presumably because of its higher structural flexibility,and retained the ability of native SP-B to stabilize DPPC interfacial films compressed to pressures near collapse against spontaneous relaxation.SP-Br also mimicked the behavior of native SP-B in lipid-protein films subjected to dynamic compression-expansion cycling in a captive bubble surfactometer,but only in the presence of phosphatidylglycerol (PG),the main anionic phospholipid in surfactant.The presence of PG appears to be required for SP-Br to acquire the appropriate tertiary folding to produce progressively more efficient lipid-protein films capable of reaching very high pressures upon limited compression with almost no hysteresis.
机译：肺表面活性剂蛋白SP-B是肺泡中表面活性剂正常功能所必需的，并且是用于治疗呼吸道疾病的治疗性表面活性剂制剂的重要组成部分。探讨成熟SP-B氨基酸序列中固有的结构和功能决定因素猪SP-B在高度变性的条件下进行了广泛的二硫键还原反应，并进行了半胱氨酸羧酰胺甲基化反应，并表征了该修饰形式的结构，脂质-蛋白质相互作用和表面活性。 SP-Br）具有与天然二硫键连接的SP-B二聚体几乎相同的二级结构。还原的SP-Br与天然SP-B相比，具有更高的结构柔韧性，这表明荧光发射对丙烯酰胺和丙烯酰胺淬灭的敏感性更高。蛋白质与脂质双层和单层相互作用期间的双相行为。与天然SP-B的相似之处在于二棕榈酰磷脂酰胆碱（DPPC）双层的热致性。SP-Br比天然SP-B在促进磷脂双层进入界面膜中的界面吸附更有效，大概是由于其较高的结构柔性，并保留了天然SP-B稳定被压缩至接近崩溃的压力的DPPC界面膜以防止自发松弛的能力。SP-Br还模拟了天然SP-B在脂蛋白膜中的动态压缩-膨胀循环中的行为气泡表面张力计，但仅在表面活性剂中主要阴离子磷脂磷脂酰甘油（PG）存在的情况下。SP-Br似乎必须具备PG的存在，才能获得适当的三级折叠，从而逐步制备出效率更高的脂蛋白膜。在有限的压缩下达到非常高的压力，几乎没有滞后。

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