Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India.
PLoS One. 2012;7(5):e36714. doi: 10.1371/journal.pone.0036714. Epub 2012 May 9.
Genome sequence of Serratia proteamaculans 568 revealed the presence of three family 33 chitin binding proteins (CBPs). The three Sp CBPs (Sp CBP21, Sp CBP28 and Sp CBP50) were heterologously expressed and purified. Sp CBP21 and Sp CBP50 showed binding preference to β-chitin, while Sp CBP28 did not bind to chitin and cellulose substrates. Both Sp CBP21 and Sp CBP50 were synergistic with four chitinases from S. proteamaculans 568 (Sp ChiA, Sp ChiB, Sp ChiC and Sp ChiD) in degradation of α- and β-chitin, especially in the presence of external electron donor (reduced glutathione). Sp ChiD benefited most from Sp CBP21 or Sp CBP50 on α-chitin, while Sp ChiB and Sp ChiD had major advantage with these Sp CBPs on β-chitin. Dose responsive studies indicated that both the Sp CBPs exhibit synergism ≥ 0.2 µM. The addition of both Sp CBP21 and Sp CBP50 in different ratios to a synergistic mixture did not significantly increase the activity. Highly conserved polar residues, important in binding and activity of CBP21 from S. marcescens (Sm CBP21), were present in Sp CBP21 and Sp CBP50, while Sp CBP28 had only one such polar residue. The inability of Sp CBP28 to bind to the test substrates could be attributed to the absence of important polar residues.
聚生肠杆菌 568 基因组序列揭示了三种家族 33 几丁质结合蛋白（CBPs）的存在。三种 Sp CBPs（Sp CBP21、Sp CBP28 和 Sp CBP50）被异源表达和纯化。Sp CBP21 和 Sp CBP50 对 β-几丁质表现出结合偏好，而 Sp CBP28 不结合几丁质和纤维素底物。Sp CBP21 和 Sp CBP50 与聚生肠杆菌 568 的四种几丁质酶（Sp ChiA、Sp ChiB、Sp ChiC 和 Sp ChiD）协同作用，降解 α-和 β-几丁质，特别是在存在外部电子供体（还原型谷胱甘肽）时。Sp ChiD 从 Sp CBP21 或 Sp CBP50 对 α-几丁质受益最大，而 Sp ChiB 和 Sp ChiD 则在 β-几丁质上具有这些 Sp CBPs 的主要优势。剂量响应研究表明，两种 Sp CBPs 均表现出协同作用≥0.2µM。将 Sp CBP21 和 Sp CBP50 以不同比例添加到协同混合物中，不会显著增加活性。聚生肠杆菌 568 中 Sp CBP21 和 Sp CBP50 存在高度保守的极性残基，对结合和活性很重要，而 Sp CBP28 只有一个这样的极性残基。Sp CBP28 不能结合测试底物，可能归因于缺乏重要的极性残基。
