The Number of Subunits Comprising the Channel Formed by the T Domain of Diphtheria Toxin
نویسندگان
چکیده
In the presence of a low pH environment, the channel-forming T domain of diphtheria toxin undergoes a conformational change that allows for both its own insertion into planar lipid bilayers and the translocation of the toxin's catalytic domain across them. Given that the T domain contributes only three transmembrane segments, and the channel is permeable to ions as large as glucosamine(+) and NAD(-), it would appear that the channel must be a multimer. Yet, there is substantial circumstantial evidence that the channel may be formed from a single subunit. To test the hypothesis that the channel formed by the T domain of diphtheria toxin is monomeric, we made mixtures of two T domain constructs whose voltage-gating characteristics differ, and then observed the gating behavior of the mixture's single channels in planar lipid bilayers. One of these constructs contained an NH(2)-terminal hexahistidine (H6) tag that blocks the channel at negative voltages; the other contained a COOH-terminal H6 tag that blocks the channel at positive voltages. If the channel is constructed from multiple T domain subunits, one expects to see a population of single channels from this mixture that are blocked at both positive and negative voltages. The observed single channels were blocked at either negative or positive voltages, but never both. Therefore, we conclude that the T domain channel is monomeric.
منابع مشابه
Design and Production of Recombinant TAT Protein Structure, Catalytic Domain of Diphtheria Toxin, and Evaluation of Its Effect on Cell Line
Background and Objectives: Cancer is one of the most deadly diseases in the present age and its conventional therapies have had low success. Toxin therapy of cancer is a new therapeutic approach, which has attracted the attention of pharmaceutical specialists. Diphtheria toxin consists of three functional, transducing, and binding domains, that the functional part inhibits protein synthesis and...
متن کاملProbing the Structure of the Diphtheria Toxin Channel
Previous work has established that the 61 amino acid stretch from residue 322 to 382 in the T-domain of diphtheria toxin forms channels indistinguishable in ion-conducting properties from those formed by the entire T-domain. In the crystal structure of the toxin's water-soluble form, the bulk of this stretch is an alpha-helical hairpin, designated TH8-9. The present study was directed at determ...
متن کاملShort Communication: Diphtheria Toxin Repressor (dtxR) Gene-based Genetic Diversity of Corynebacterium diphtheriae isolated in Jakarta, Indonesia, 2018-2019
Background and Objective: In Indonesia, diphtheria cases caused by Corynebacterium diphtheriae are still occurring until today. One of the causes is probably the diphtheria toxin repressor (dtxR) gene which influences toxin expression. Therefore, in this study the characterization of the gene was performed to determine the mutations that affect the DtxR protein. Methods: The dtxR genes of ...
متن کاملProduction of Chicken Egg Yolk Antibody (IgY) Against Recombinant Cholera Toxin B Subunit and Evaluation of Its Prophylaxis Potency in Mice
Background: Cholera toxin (CT), responsible for the harmful effects of cholera infection, is made up of one A subunit (enzymatic), and five B subunits (cell binding). The release of cholera toxin is the main reason for the debilitating loss of intestinal fluid. Inhibition of the B subunit (CTB) may block CT activity. Objective: To determine the effect of anti CTB-IgY against oral challenge with...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- The Journal of General Physiology
دوره 118 شماره
صفحات -
تاریخ انتشار 2001