Noncovalent Shiga-like Toxin Assemblies: Characterization by Means of Mass Spectrometry and Tandem Mass Spectrometry

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• 作者：Jonathan P. Williams ; Brian N. Green ; Daniel C. Smith ; Keith R. Jennings ; Katherine A. H. Moore ; Susan E. Slade ; Lynne M. Roberts ; and James H. Scrivens
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：June 14, 2005
• 年：2005
• 卷：44
• 期：23
• 页码：8282 - 8290
• 全文大小：418K
• 年卷期：v.44,no.23(June 14, 2005)
• ISSN：1520-4995

文摘

Shiga-like toxin 1 (SLTx), produced by enterohemorrhagic strains of Escherichia coli (EHEC),belongs to a family of structurally and functionally related AB₅ protein toxins that are associated withhuman disease. EHEC infection often gives rise to hemolytic colitis, while toxin-induced kidney damageis one of the major causes of hemolytic uremic syndrome (HUS) and acute renal failure in children. Assuch, an understanding and analysis of the noncovalent interactions that maintain the quaternary structureof this toxin are fundamentally important since such interactions have significant biochemical and medicalimplications. This paper reports on the analysis of the noncovalent homopentameric complex of Shiga-like toxin B chain (SLTx-B₅) using electrospray ionization (ESI) triple-quadrupole (QqQ) mass spectrometry(MS) and tandem mass spectrometry (MS/MS) and the analysis of the noncovalent hexameric holotoxin(SLTx-AB₅) using ESI time-of-flight (TOF) MS. The triple-quadrupole analysis revealed highly chargedmonomer ions dissociate from the multiprotein complex to form dimer, trimer, and tetramer product ions,which were also seen to further dissociate. The ESI-TOFMS analysis of SLTx-AB₅ revealed the complexremained intact and was observed in the gas phase over a range of pHs. Theses findings demonstrate thatthe gas-phase structure observed for both the holotoxin and the isoloated B chains correlates well withthe structures reported to exist in the solution phase for these proteins. Such analysis provides a rapidscreening technique for assessing the noncovalent structure of this family of proteins and other structurallyrelated toxins.