Interface mutation in heptameric co-chaperonin protein 10 destabilizes subunits but not interfaces.
We here report on a human mitochondrial co-chaperonin protein 10 (cpn10) variant in which the conserved interface residue leucine-96 is replaced with glycine (Leu96Gly cpn10). According to analytical ultracentrifugation, the mutation does not perturb the ability to assemble into a heptamer and electron microscopy reveals that Leu96Gly cpn10 is ring-shaped like wild-type cpn10. Despite elimination of a hydrophobic residue, the subunit-subunit affinity is essentially identical in Leu96Gly cpn10 and in wild-type cpn10. This is explained by a compensating rearrangement in Leu96Gly cpn10, evident from cross-linking and gel-filtration experiments. As a direct result of lower monomer stability, Leu96Gly cpn10 is dramatically less stable towards chemical and thermal perturbations as compared to wild-type cpn10. We conclude that leucine-96 is an interface residue preserved to guarantee stable cpn10 monomers. Our study demonstrates that the cpn10 interfaces can adapt to structural alterations without loss of either subunit-subunit affinity or heptamer specificity.
Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251, USA.
Christopher
C
Brown
Jue
J
Liao
Pernilla
P
Wittung-Stafshede
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D018835:Chaperonin 10 / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D002942:Circular Dichroism; D017124:Conserved Sequence; D003432:Cross-Linking Reagents / Q000737:chemistry; D019281:Dimerization; D005453:Fluorescence; D005998:Glycine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019791:Guanidine / Q000737:chemistry; D006801:Humans; D007930:Leucine / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D021122:Protein Subunits; D014461:Ultracentrifugation / Q000379:methods; D014508:Urea / Q000737:chemistry
D018835:Chaperonin 10; D003432:Cross-Linking Reagents; D021122:Protein Subunits; D014508:Urea; D007930:Leucine; D019791:Guanidine; D005998:Glycine