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Publication Abstract from PubMed

Protein nanostructures have been gaining in interest, along with developments in new methods for construction of novel nanostructures. We have previously shown that c-type cytochromes and myoglobin form oligomers by domain swapping. Herein, we show that a four-helix bundle protein cyt cb(562), with the cyt b(562) heme attached to the protein moiety by two Cys residues insertion, forms a domain-swapped dimer. Dimeric cyt cb(562) did not dissociate to monomers at 4 degrees C, whereas dimeric cyt b(562) dissociated under the same conditions, showing that heme attachment to the protein moiety stabilizes the domain-swapped structure. According to X-ray crystallographic analysis of dimeric cyt cb(562), the two helices in the N-terminal region of one protomer interacted with the other two helices in the C-terminal region of the other protomer, where Lys51-Asp54 served as a hinge loop. The heme coordination structure of the dimer was similar to that of the monomer. In the crystal, three domain-swapped cyt cb(562) dimers formed a unique cage structure with a Zn-SO(4) cluster inside the cavity. The Zn-SO(4) cluster consisted of fifteen Zn(2+) and seven SO(4)(2-) ions, whereas six additional Zn(2+) ions were detected inside the cavity. The cage structure was stabilized by coordination of the amino acid side chains of the dimers to the Zn(2+) ions and connection of two four-helix bundle units through the conformation-adjustable hinge loop. These results show that domain swapping can be applied in the construction of unique protein nanostructures.

Domain-swapped cytochrome cb(562) dimer and its nanocage encapsulating a Zn-SO(4) cluster in the internal cavity.,Miyamoto T, Kuribayashi M, Nagao S, Shomura Y, Higuchi Y, Hirota S Chem Sci. 2015 Dec 1;6(12):7336-7342. doi: 10.1039/c5sc02428e. Epub 2015 Sep 22. PMID:28791095^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.