申请人:——
公开号:US20030022178A1
公开(公告)日:2003-01-30
The present invention is a substantially purified sortase-transamidase enzyme from Gram-positive bacteria, such as
Staphylococcus aureus
. The enzyme having a molecular weight of about 23,539 or about 29,076 daltons and catalyzing a reaction that covalently cross-links the carboxyl terminus of a protein having a sorting signal to the peptidoglycan of a Gram-positive bacterium, the sorting signal having: (1) a motif of LPX
3
X
4
G therein; (2) a substantially hydrophobic domain of at least 31 amino acids carboxyl to the motif; and (3) a charged tail region with at least two positively charged residues carboxyl to the substantially hydrophobic domain, at least one of the two positively charged residues being arginine, the two positively charged residues being located at residues 31-33 from the motif, wherein X
3
is any of the twenty naturally-occurring L-amino acids and X
4
is selected from the group consisting of alanine, serine, and threonine, and wherein sorting occurs by cleavage between the fourth and fifth residues of the LPX
3
X
4
G motif. Variants of the enzyme, methods for cloning the gene encoding the enzyme and expressing the cloned gene, and methods of use of the enzyme, including for screening for antibiotics and for display of proteins or peptides on the surfaces of Gram-positive bacteria, are also disclosed.
本发明是一种从革兰氏阳性细菌(如
金黄色葡萄球菌
.该酶的分子量约为 23,539 或 29,076 道尔顿,可催化将具有分选信号的蛋白质的羧基端与革兰氏阳性细菌的肽聚糖共价交联的反应,分选信号具有:(1) LPX
3
X
4
G的基序;(2) 与基序羧基化的至少有 31 个氨基酸的基本疏水结构域;(3) 与基本疏水结构域羧基化的至少有两个带正电的残基的带电尾区,这两个带正电的残基中至少有一个是精氨酸,这两个带正电的残基位于基序的残基 31-33 处,其中 X
3
是二十种天然存在的 L-氨基酸中的任何一种,X
4
选自丙氨酸、丝氨酸和苏氨酸组成的组,其中分选通过 LPX 的第四和第五个残基之间的裂解进行
3
X
4
G motif。此外,还公开了该酶的变体、克隆编码该酶的基因和表达克隆基因的方法,以及该酶的使用方法,包括用于筛选抗生素和在革兰氏阳性细菌表面显示蛋白质或肽的方法。