2ll8

Publication Abstract from PubMed

The solution nuclear magnetic resonance (NMR) structures and backbone (15)N dynamics of the specialized acyl carrier protein (ACP), RpAcpXL, from Rhodopseudomonas palustris, in both the apo form and holo form modified by covalent attachment of 4'-phosphopantetheine at S37, are virtually identical, monomeric, and correspond to the closed conformation. The structures have an extra alpha-helix compared to the archetypical ACP from Escherichia coli, which has four helices, resulting in a larger opening to the hydrophobic cavity. Chemical shift differences between apo- and holo-RpAcpXL indicated some differences in the hinge region between alpha2 and alpha3 and in the hydrophobic cavity environment, but corresponding changes in nuclear Overhauser effect cross-peak patterns were not detected. In contrast to the NMR structures, apo-RpAcpXL was observed in an open conformation in crystals that diffracted to 2.0 A resolution, which resulted from movement of alpha3. On the basis of the crystal structure, the predicted biological assembly is a homodimer. Although the possible biological significance of dimerization is unknown, there is potential that the resulting large shared hydrophobic cavity could accommodate the very long-chain fatty acid (28-30 carbons) that this specialized ACP is known to synthesize and transfer to lipid A. These structures are the first representatives of the AcpXL family and the first to indicate that dimerization may be important for the function of these specialized ACPs.

Structure of a specialized acyl carrier protein essential for lipid A biosynthesis with very long-chain fatty acids in open and closed conformations.,Ramelot TA, Rossi P, Forouhar F, Lee HW, Yang Y, Ni S, Unser S, Lew S, Seetharaman J, Xiao R, Acton TB, Everett JK, Prestegard JH, Hunt JF, Montelione GT, Kennedy MA Biochemistry. 2012 Sep 18;51(37):7239-49. doi: 10.1021/bi300546b. Epub 2012 Sep, 7. PMID:22876860^[1]

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