Tarentino A L, Quinones G, Changchien L M, Plummer T H
Division of Clinical Sciences, Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509.
J Biol Chem. 1993 May 5;268(13):9702-8.
The genes for Flavobacterium meningosepticum Endo (endoglycosidase) F2 and Endo F3 were cloned, and their nucleotide sequences were determined. The deduced amino acid sequences were verified independently to a large extent by direct peptide microsequencing of 66 and 84% of native Endo F2 and Endo F3, respectively. Structurally, the Endo F2 and Endo F3 genes code for a typically long leader sequence of 45 and 39 amino acids, respectively, and, in both cases, a mature protein of 290 amino acids. Comparative structural analysis demonstrated minimum overall homology (15-30%) between Endo F1, Endo F2, and Endo F3, but revealed distinct clusters of identical residues distributed throughout the entire sequence, which represent motifs for binding and hydrolysis of beta 1,4-di-N-acetylchitobiosyl linkages in complex carbohydrates. The mobility of native Endo F2 and Endo F3 on SDS-polyacrylamide gel electrophoresis, unlike Endo F1, did not correlate with the molecular weights determined from the coding region of the corresponding genes. Mass spectrometry confirmed that Endo F2 and Endo F3 were heterogeneous and contained approximately 4000 and 1200 daltons of mass not accounted for in the gene structure. We presume that Endo F2 and Endo F3 are variably post-translationally modified during secretion by possible linkage to the hydroxyl of serine.
脑膜炎败血黄杆菌内切（内切糖苷酶）F2和内切酶F3的基因被克隆，并测定了它们的核苷酸序列。推导的氨基酸序列分别通过对天然内切酶F2和内切酶F3的66%和84%进行直接肽微测序在很大程度上得到了独立验证。在结构上，内切酶F2和内切酶F3基因分别编码一个典型的长45和39个氨基酸的前导序列，并且在这两种情况下，编码一个290个氨基酸的成熟蛋白。比较结构分析表明，内切酶F1、内切酶F2和内切酶F3之间的总体同源性最低（15%-30%），但揭示了在整个序列中分布的不同的相同残基簇，这些残基簇代表了复杂碳水化合物中β1,4-二-N-乙酰壳二糖键结合和水解的基序。与内切酶F1不同，天然内切酶F2和内切酶F3在SDS-聚丙烯酰胺凝胶电泳上的迁移率与从相应基因编码区确定的分子量不相关。质谱证实，内切酶F2和内切酶F3是异质的，并且含有约4000和1200道尔顿的质量，这在基因结构中未得到解释。我们推测，内切酶F2和内切酶F3在分泌过程中可能通过与丝氨酸羟基的连接而发生可变的翻译后修饰。
