The Y42H mutation in medium-chain acyl-CoA dehydrogenase, which is prevalent in babies identified by MS/MS-based newborn screening, is temperature sensitive.
Medium-chain acyl-CoA dehydrogenase (MCAD) is a homotetrameric flavoprotein which catalyses the initial step of the beta-oxidation of medium-chain fatty acids. Mutations in MCAD may cause disease in humans. A Y42H mutation is frequently found in babies identified by newborn screening with MS/MS, yet there are no reports of patients presenting clinically with this mutation. As a basis for judging its potential consequences we have examined the protein phenotype of the Y42H mutation and the common disease-associated K304E mutation. Our studies of the intracellular biogenesis of the variant proteins at different temperatures in isolated mitochondria after in vitro translation, together with studies of cultured patient cells, indicated that steady-state levels of the Y42H variant in comparison to wild-type were decreased at higher temperature though to a lesser extent than for the K304E variant. To distinguish between effects of temperature on folding/assembly and the stability of the native enzyme, the thermal stability of the variant proteins was studied after expression and purification by dye affinity chromatography. This showed that, compared with the wild-type enzyme, the thermostability of the Y42H variant was decreased, but not to the same degree as that of the K304E variant. Substrate binding, interaction with the natural electron acceptor, and the binding of the prosthetic group, FAD, were only slightly affected by the Y42H mutation. Our study suggests that Y42H is a temperature sensitive mutation, which is mild at low temperatures, but may have deleterious effects at increased temperatures.
Department of Biochemistry and the Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Ireland. brage@ki.au.dk
Linda
L
O'Reilly
Peter
P
Bross
Thomas J
TJ
Corydon
Simon E
SE
Olpin
Jakob
J
Hansen
John M
JM
Kenney
Shawn E
SE
McCandless
Dianne M
DM
Frazier
Vibeke
V
Winter
Niels
N
Gregersen
Paul C
PC
Engel
Brage Storstein
BS
Andresen
D042964:Acyl-CoA Dehydrogenase / Q000737:chemistry / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D019943:Amino Acid Substitution; D000818:Animals; D002942:Circular Dichroism / Q000379:methods; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D018698:Glutamic Acid / Q000235:genetics; D006639:Histidine / Q000235:genetics; D006801:Humans; D007231:Infant, Newborn; D008214:Lymphocytes / Q000166:cytology / Q000378:metabolism; D008239:Lysine / Q000235:genetics; D008930:Mitochondria, Liver / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D019814:Myristic Acid / Q000378:metabolism; D015997:Neonatal Screening; D010084:Oxidation-Reduction; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000235:genetics
D011994:Recombinant Proteins; D019814:Myristic Acid; D018698:Glutamic Acid; D014443:Tyrosine; D006639:Histidine; D042964:Acyl-CoA Dehydrogenase; D008239:Lysine