Bacillus cereus sphingomyelinase recognizes ganglioside GM3
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- 作者：Masataka Oda ; masa@ph.bunri-u.ac.jp ; Aoi Fujita ; Kensuke Okui ; Kazuaki Miyamoto ; Masahiro Shibutani ; Teruhisa Takagishi ; Masahiro Nagahama
- 关键词：B. cereus ; Bacillus cereus ; SMase ; sphingomyelinase ; Bc-SMase ; Bacillus cereus sphingomyelinase ; GM3 ; NeuAc¦Á2-3Gal¦Â1-4Glc¦Â1-1ceramide ; SPR ; surface plasmon resonance
- 刊名：Biochemical and Biophysical Research Communications
- 出版年：2013
- 出版时间：8 February, 2013
- 年：2013
- 卷：431
- 期：2
- 页码：164-168
- 全文大小：691 K
文摘
Sphingomyelinase (SMase) from Bacillus cereus (Bc-SMase) hydrolyzes sphingomyelin (SM) to phosphocholine and ceramide in a divalent metal ion-dependent manner, and is a virulence factor for septicemia. Bc-SMase has three characteristic sites, viz., the central site (catalytic site), side-edge site (membrane binding site), and ¦Â-hairpin region (membrane binding site). Here, we show that the ¦Â-hairpin directly binds to gangliosides, especially NeuAc¦Á2-3Gal¦Â1-4Glc¦Â1-1ceramide (GM3) through a carbohydrate moiety. Neuraminidase inhibited the binding of Bc-SMase to mouse peritoneal macrophages in a dose-dependent manner. SPR analysis revealed that the binding response of Bc-SMase to liposomes containing GM3 was about 15-fold higher than that to liposomes lacking GM3. Moreover, experiments with site-directed mutants indicated that Trp-284 and Phe-285 in the ¦Â-hairpin play an important role in the interaction with GM3. The binding of W284A and F285A mutant enzymes to mouse macrophages decreased markedly in comparison to the binding by wild-type enzymes. Therefore, we conclude that GM3 is the primary cellular receptor for Bc-SMase, and that the ¦Â-hairpin region is the tethering region for gangliosides.