A new basic protein, designated ligatoxin B, containing 46 amino acid residues has been isolated from the mistletoe Phoradendron liga (Gill.) Eichl. (Viscaceae). The protein's primary structure, determined unambiguously using a combination of automated Edman degradation, trypsin enzymic digestion, and tandem MS analysis, was 1–KSCCPSTTAR–NIYNTCRLTG–ASRSVCASLS–GCKIISGSTC–DSGWNH–46. Ligatoxin B exhibited in vitro cytotoxic activities on the human lymphoma cell line U-937-GTB and the primary multidrug-resistant renal adenocarcinoma cell line ACHN, with IC50 values of 1.8μM and 3.2μM respectively. Sequence alignment with other thionins identified a new member of the class 3 thionins, ligatoxin B, which is similar to the earlier described ligatoxin A. As predicted by the method of homology modelling, ligatoxin B shares a three-dimensional structure with the viscotoxins and purothionins and so may have the same mode of cytotoxic action. The novel similarities observed by structural comparison of the helix–turn–helix (HTH) motifs of the thionins, including ligatoxin B, and the HTH DNA-binding proteins, led us to propose the working hypothesis that thionins represent a new group of DNA-binding proteins. This working hypothesis could be useful in further dissecting the molecular mechanisms of thionin cytotoxicity and of thionin opposition to multidrug resistance, and useful in clarifying the physiological function of thionins in plants.
Skip Nav Destination
Article navigation
September 2002
- PDF Icon PDF LinkFront Matter
Research Article|
September 01 2002
Ligatoxin B, a new cytotoxic protein with a novel helix–turn–helix DNA-binding domain from the mistletoe Phoradendron liga
Shi-Sheng LI;
Shi-Sheng LI
∗Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala Biomedical Center, PO Box 574, SE-751 23, Uppsala, Sweden,
Search for other works by this author on:
Joachim GULLBO;
Joachim GULLBO
†Division of Clinical Pharmacology, University Hospital, Uppsala University, SE-751 85, Uppsala, Sweden
Search for other works by this author on:
Petra LINDHOLM;
Petra LINDHOLM
∗Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala Biomedical Center, PO Box 574, SE-751 23, Uppsala, Sweden,
Search for other works by this author on:
Rolf LARSSON;
Rolf LARSSON
†Division of Clinical Pharmacology, University Hospital, Uppsala University, SE-751 85, Uppsala, Sweden
Search for other works by this author on:
Eva THUNBERG;
Eva THUNBERG
∗Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala Biomedical Center, PO Box 574, SE-751 23, Uppsala, Sweden,
Search for other works by this author on:
Gunnar SAMUELSSON;
Gunnar SAMUELSSON
∗Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala Biomedical Center, PO Box 574, SE-751 23, Uppsala, Sweden,
Search for other works by this author on:
Lars BOHLIN;
Lars BOHLIN
∗Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala Biomedical Center, PO Box 574, SE-751 23, Uppsala, Sweden,
Search for other works by this author on:
Per CLAESON
Per CLAESON
1
∗Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala Biomedical Center, PO Box 574, SE-751 23, Uppsala, Sweden,
1To whom correspondence should be addressed (e-mail per.claeson@mpa.se).
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
February 04 2002
Revision Received:
May 22 2002
Accepted:
June 06 2002
Accepted Manuscript online:
June 06 2002
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London ©2002
2002
Biochem J (2002) 366 (2): 405–413.
Article history
Received:
February 04 2002
Revision Received:
May 22 2002
Accepted:
June 06 2002
Accepted Manuscript online:
June 06 2002
Citation
Shi-Sheng LI, Joachim GULLBO, Petra LINDHOLM, Rolf LARSSON, Eva THUNBERG, Gunnar SAMUELSSON, Lars BOHLIN, Per CLAESON; Ligatoxin B, a new cytotoxic protein with a novel helix–turn–helix DNA-binding domain from the mistletoe Phoradendron liga. Biochem J 1 September 2002; 366 (2): 405–413. doi: https://doi.org/10.1042/bj20020221
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Captcha Validation Error. Please try again.