Structural highlights
Publication Abstract from PubMedAbundant and essential motifs, such as phosphate-binding loops (P-loops), are presumed to be the seeds of modern enzymes. The Walker-A P-loop is absolutely essential in modern NTPase enzymes, in mediating binding, and transfer of the terminal phosphate groups of NTPs. However, NTPase function depends on many additional active-site residues placed throughout the protein's scaffold. Can motifs such as P-loops confer function in a simpler context? We applied a phylogenetic analysis that yielded a sequence logo of the putative ancestral Walker-A P-loop element: a beta-strand connected to an alpha-helix via the P-loop. Computational design incorporated this element into de novo designed beta-alpha repeat proteins with relatively few sequence modifications. We obtained soluble, stable proteins that unlike modern P-loop NTPases bound ATP in a magnesium-independent manner. Foremost, these simple P-loop proteins avidly bound polynucleotides, RNA, and single-strand DNA, and mutations in the P-loop's key residues abolished binding. Binding appears to be facilitated by the structural plasticity of these proteins, including quaternary structure polymorphism that promotes a combined action of multiple P-loops. Accordingly, oligomerization enabled a 55-aa protein carrying a single P-loop to confer avid polynucleotide binding. Overall, our results show that the P-loop Walker-A motif can be implemented in small and simple beta-alpha repeat proteins, primarily as a polynucleotide binding motif. Simple yet functional phosphate-loop proteins.,Romero Romero ML, Yang F, Lin YR, Toth-Petroczy A, Berezovsky IN, Goncearenco A, Yang W, Wellner A, Kumar-Deshmukh F, Sharon M, Baker D, Varani G, Tawfik DS Proc Natl Acad Sci U S A. 2018 Nov 30. pii: 1812400115. doi:, 10.1073/pnas.1812400115. PMID:30504143[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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This page was last modified 08:49, 19 December 2018.