Restoration of lectin activity to an inactive abrin B chain by substitution and mutation of the 2 gamma subdomain
UNSPECIFIED. (1999) Restoration of lectin activity to an inactive abrin B chain by substitution and mutation of the 2 gamma subdomain. EUROPEAN JOURNAL OF BIOCHEMISTRY, 260 (2). pp. 355-361. ISSN 0014-2956Full text not available from this repository.
Abrin is a heterodimeric plant protein that occurs in several isoforms (abrin-a, abrin-b, abrin-c and abrin-d), whose B chains are believed to either have (abrin-a and abrin-d) or lack (abrin-b and abrin-c) the ability to bind galactose. The 5' signal sequence and toxin B chain (ATB)-coding region were excised from a preproabrin cDNA [K. A. Wood J. M. Lord, E. J. Wawrzynczak, and M. Piatak (1991) Eur J. Biochem. 198, 723-732], tentatively identified as abrin-c, which was predicted to lack lectin activity, and fused in-frame to generate pre-ATE cDNA. Transcripts, synthesized in vitro from pre-ATE cloned into the transcription vector pSP64T, were expressed after microinjection into Xenopus oocytes. The recombinant ATE was shown, using a qualitative sugar-binding assay, to be devoid of lectin activity. Lectin activity could not be restored to this nonbinding ATE by replacing the 2 gamma subdomain with the corresponding galactose-binding 2 gamma subdomain from ricin B chain, but it was restored by replacement with the active galactose-binding 2 gamma subdomain from a different abrin isoform (abrin-a). The putative galactose-binding pocket of the nonbinding ATE 2 gamma subdomain contained a His residue at the position occupied by a residue with an aromatic side chain (Tyr or Trp) in functional 2 gamma subdomains. Mutationally converting this His to either Tyr or Trp restored lectin activity to the nonbinding ATE, emphasizing the contribution of an aromatic side chain in a functional 2 gamma subdomain galactose-binding site for members of this lectin family.
|Item Type:||Journal Article|
|Subjects:||Q Science > QD Chemistry|
|Journal or Publication Title:||EUROPEAN JOURNAL OF BIOCHEMISTRY|
|Publisher:||BLACKWELL SCIENCE LTD|
|Number of Pages:||7|
|Page Range:||pp. 355-361|
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