Crystal structure determination of an unknown protein with putative acetyltransferase function. (South Carolina Academy of Sciences Abstracts).
During our efforts to crystallize human sperm protein Sp17, we have
obtained cubic crystals belonging to the space group F432 with a=219.34
[Angstrom]. The crystal structure has been determined at 2.2 [Angstrom]
resolution using .the multiple isomorphous replacement/anomalous
scattering (MIRAS) method based on [Sm.sup.3+] and [Yb.sup.3+]
derivatives. Examination of the electron density maps revealed that the
protein is not SP17. A model was built to follow the fold of the peptide
chain with amino acid side chains guessed based on the shape of electron
density. The Dali Server of EMBL was used to compare the fold of the
unknown protein to the fold of other proteins in the protein data bank.
The protein fold structurally matched with strong scores to two
acetyltransferase proteins: Azotobacter vinelandii dihydrolipoamide
acetyltransferase and Escherichia coli chloramphenicol
acetyltransferase. The protein forms 24-mer capsules in the crystals
that may be used to engineer a variety of catalytic functions.
Re-examination of the purification process showed that in some
preparations SDS-PAGE revealed a contamination band. These contaminated
preps actually yielded crystals despite the fact that Sp 17 was the
dominant protein. This research was supported by a grant from the USC NanoCenter.
Jie Qin, Leslie Lovelace, Jason Phan, R. Bruce Dunlap, L. Lebioda
Department of Chemistry and Biochemistry, University of South Carolina