Document Detail

Structural features of recombinant MMADHC isoforms and their interactions with MMACHC, proteins of mammalian vitamin B(12) metabolism.
MedLine Citation:
PMID:  22832074     Owner:  NLM     Status:  Publisher    
The genes MMACHC and MMADHC encode critical proteins involved in the intracellular metabolism of cobalamin. Two clinical features, homocystinuria and methylmalonic aciduria, define inborn errors of these genes. Based on disease phenotypes, MMADHC acts at a branch point for cobalamin delivery, apparently exerting its function through interaction with MMACHC that demonstrates dealkylase and decyanase activities. Here we present biophysical analyses of MMADHC to identify structural features and to further characterize its interaction with MMACHC. Two recombinant tag-less isoforms of MMADHC (MMADHCΔ1-12 and MMADHCΔ1-61) were expressed and purified. Full length MMACHC and full length MMADHC were detected in whole cell lysates of human cells; by Western blotting, their molecular masses corresponded to purified recombinant proteins. By clear-native PAGE and by dynamic light scattering, recombinant MMADHCs were stable and monodisperse. Both species were monomeric, adopting extended conformations in solution. Circular dichroism and secondary structure predictions correlated with significant regions of disorder within the N-terminal domain of MMADHC. We found no evidence that MMADHC binds cobalamin. Phage panning against MMADHC predicted four binding regions on MMACHC, two of which overlap with predicted sites on MMACHC at which it may self-associate. Specific, concentration-dependent responses were observed for MMACHC binding to itself and to both MMADHC constructs. As estimated in the sub-micromolar range, the binding of MMACHC to itself was weaker compared to its interaction with either of the MMADHC isoforms. We propose that the function of MMADHC is exerted through its structured C-terminal domain via interactions with MMACHC.
Justin C Deme; Isabelle R Miousse; Maria Plesa; Jaeseung C Kim; Mark A Hancock; Wayne Mah; David S Rosenblatt; James W Coulton
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-11
Journal Detail:
Title:  Molecular genetics and metabolism     Volume:  -     ISSN:  1096-7206     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-26     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9805456     Medline TA:  Mol Genet Metab     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 Elsevier Inc. All rights reserved.
Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada.
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