Synthesis and characterization of a 25-residue rubredoxin(II)-like metalloprotein and its valine-leucine mutant.

An iron-sulfur metalloprotein containing the 5-12 and 35-50 residues of Desulfovibrio gigas rubredoxin has been synthesized by Fmoc solid phase peptide synthesis and subsequent peptide folding. A Gly links the two residue chains between Val-5 and Glu-50. Sybyl Tripos structure optimization indicates only minor structural changes of the folded synthetic protein compared to the similar residue positions in the native protein. The UV-VIS spectrum of the reduced synthetic protein is very similar to that of native D. gigas rubredoxin and the molecular mass determined by laser mass spectrometry has the expected value (+/- 2D). No metal is transferred to the gas phase by the laser beam merely by mixing the peptide and iron(II), substantiating that the folding procedure is a necessary pre-requisite for protein formation. The Val-->Leu41 chemical mutant has also been synthesized and behaves in a closely similar fashion.