UNSPECIFIED. (2002) Binding of ricin A-chain to negatively charged phospholipid vesicles leads to protein structural changes and destabilizes the lipid bilayer. BIOCHEMISTRY, 41 (8). pp. 2836-2843. ISSN 0006-2960

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Abstract

Ricin is a heterodimeric protein toxin in which a catalytic polypeptide (the A-chain or RTA) is linked by a disulfide bond to a cell-binding polypeptide (the B-chain or RTB). During cell entry, ricin undergoes retrograde vesicular transport to reach the endoplasmic reticulum (ER) lumen, from where RTA translocates into the cytosol, probably by masquerading as a substrate for the ER-associated protein degradation (ERAD) pathway. In partitioning studies in Triton X-114 solution, RTA is predominantly found in the detergent phase, whereas ricin holotoxin, native RTB, and several single-chain ribosome-inactivating proteins (RIPS) are in the aqueous phase. Fluorescence spectroscopy and far-UV circular dichroism (CD) demonstrated significant structural changes in RTA as a result of its interaction with liposomes containing negatively charged phospholipid (POPG). These lipid-induced structural changes markedly increased the trypsin sensitivity of RTA and, on the basis of the protein fluorescence determinations, abolished its ability to bind to adenine, the product resulting from RTA-catalyzed depurination of 28S ribosomal RNA. RTA also released trapped calcein from POPG vesicles, indicating that it destabilized the lipid bilayer. We speculate that membrane-induced partial unfolding of RTA during cell entry may facilitate its recognition as an ERAD substrate.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry
Journal or Publication Title:	BIOCHEMISTRY
Publisher:	AMER CHEMICAL SOC
ISSN:	0006-2960
Date:	26 February 2002
Volume:	41
Number:	8
Number of Pages:	8
Page Range:	pp. 2836-2843
Identification Number:	10.1021/bi012012i
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/11239

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