5AO4

Crystal structure of in vitro phosphorylated human SAMHD1 (amino acid residues 115-626) bound to GTP

Summary for 5AO4

• Entry DOI: 10.2210/pdb5ao4/pdb
• Related: 5AO0 5AO1 5AO2 5AO3
• Descriptor: DEOXYNUCLEOSIDE TRIPHOSPHATE TRIPHOSPHOHYDROLASE SAMHD1, FE (III) ION, GUANOSINE-5'-TRIPHOSPHATE (3 entities in total)
• Functional Keywords: hydrolase, deoxynucleoside triphosphate triphosphohydrolase, hiv restriction factor
• Biological source: HOMO SAPIENS (HUMAN)
• Cellular location: Nucleus : Q9Y3Z3
• Total number of polymer chains: 4
• Total formula weight: 251412.66

Authors

Arnold, L.H.,Schwefel, D.,Taylor, I.A. (deposition date: 2015-09-09, release date: 2015-10-14, Last modification date: 2024-10-09)

Primary citation

Arnold, L.H.,Groom, H.C.T.,Kunzelmann, S.,Schwefel, D.,Caswell, S.J.,Ordonez, P.,Mann, M.C.,Rueschenbaum, S.,Goldstone, D.C.,Pennell, S.,Howell, S.A.,Stoye, J.P.,Webb, M.,Taylor, I.A.,Bishop, K.N.
Phospho-Dependent Regulation of Samhd1 Oligomerisation Couples Catalysis and Restriction.
Plos Pathog., 11:5194-, 2015

PubMed Abstract: SAMHD1 restricts HIV-1 infection of myeloid-lineage and resting CD4+ T-cells. Most likely this occurs through deoxynucleoside triphosphate triphosphohydrolase activity that reduces cellular dNTP to a level where reverse transcriptase cannot function, although alternative mechanisms have been proposed recently. Here, we present combined structural and virological data demonstrating that in addition to allosteric activation and triphosphohydrolase activity, restriction correlates with the capacity of SAMHD1 to form "long-lived" enzymatically competent tetramers. Tetramer disruption invariably abolishes restriction but has varied effects on in vitro triphosphohydrolase activity. SAMHD1 phosphorylation also ablates restriction and tetramer formation but without affecting triphosphohydrolase steady-state kinetics. However phospho-SAMHD1 is unable to catalyse dNTP turnover under conditions of nucleotide depletion. Based on our findings we propose a model for phosphorylation-dependent regulation of SAMHD1 activity where dephosphorylation switches housekeeping SAMHD1 found in cycling cells to a high-activity stable tetrameric form that depletes and maintains low levels of dNTPs in differentiated cells.

PubMed: 26431200
DOI: 10.1371/JOURNAL.PPAT.1005194

Experimental method

X-RAY DIFFRACTION (3.7 Å)