Raskin C, Gérard C, Donfut S, Giannotta E, Van Driessche G, Van Beeumen J, Dusart J
Centre Ingénierie des Protéines, Institut de Chimie B6a, Université de Liège, Sart Tilman, 4000 Liège, Belgium.
Cell Mol Life Sci. 2003 Jul;60(7):1460-9. doi: 10.1007/s00018-003-3008-9.
Streptomyces cacaoi beta-lactamase genes are controlled by two regulators named blaA and blaB. Whereas BlaA has been identified as a LysR-type activator, the function of BlaB is still unknown. Its primary structure is similar to that of the serine penicillin-recognizing enzymes (PREs). Indeed, the SXXK and KTG motifs are perfectly conserved in BlaB, whereas the common SXN element found in PREs is replaced by a SDG motif. Site-directed mutations were introduced in these motifs and they all disturb beta-lactamase regulation. A water-soluble form of BlaB was also overexpressed in the Streptomyces lividans TK24 cytoplasm and purified. To elucidate the activity of BlaB, several compounds recognized by PREs were tested. BlaB could be acylated by some of them, and it can therefore be considered as a penicillin-binding protein. BlaB is devoid of beta-lactamase, D-aminopeptidase, DD-carboxypeptidase or thiolesterase activity.
可可链霉菌β-内酰胺酶基因受名为blaA和blaB的两种调控因子控制。虽然BlaA已被鉴定为一种LysR型激活剂，但BlaB的功能仍然未知。其一级结构与丝氨酸青霉素识别酶（PREs）相似。实际上，SXXK和KTG基序在BlaB中完全保守，而PREs中常见的SXN元件被SDG基序取代。在这些基序中引入了定点突变，它们都干扰了β-内酰胺酶的调控。一种水溶性形式的BlaB也在变铅青链霉菌TK24细胞质中过表达并纯化。为了阐明BlaB的活性，测试了几种PREs识别的化合物。其中一些化合物可以使BlaB酰化，因此它可以被视为一种青霉素结合蛋白。BlaB没有β-内酰胺酶、D-氨基肽酶、DD-羧肽酶或硫酯酶活性。
