Structure of human NADK2 reveals atypical assembly and regulation of NAD kinases from animal mitochondria. Author Jin Du, Michael Estrella, Kristina Solorio-Kirpichyan, Philip Jeffrey, Alexei Korennykh Publication Year 2022 Type Journal Article Abstract All kingdoms of life produce essential nicotinamide dinucleotide NADP(H) using NAD kinases (NADKs). A panel of published NADK structures from bacteria, eukaryotic cytosol, and yeast mitochondria revealed similar tetrameric enzymes. Here, we present the 2.8-Å structure of the human mitochondrial kinase NADK2 with a bound substrate, which is an exception to this uniformity, diverging both structurally and biochemically from NADKs. We show that NADK2 harbors a unique tetramer disruptor/dimerization lement, which is conserved in itochondrial inases of nimals (EMKA) and absent from other NADKs. EMKA stabilizes the NADK2 dimer but prevents further NADK2 oligomerization by blocking the tetramerization interface. This structural change bears functional consequences and alters the activation mechanism of the enzyme. Whereas tetrameric NADKs undergo cooperative activation via oligomerization, NADK2 is a constitutively active noncooperative dimer. Thus, our data point to a unique regulation of NADP(H) synthesis in animal mitochondria achieved via structural adaptation of the NADK2 kinase. Keywords Animals, Humans, Phosphotransferases (Alcohol Group Acceptor), Protein Multimerization, Mitochondria, NAD, NADP, Mitochondrial Proteins Journal Proc Natl Acad Sci U S A Volume 119 Issue 26 Pages e2200923119 Date Published 2022 Jun 28 ISSN Number 1091-6490 DOI 10.1073/pnas.2200923119 Alternate Journal Proc Natl Acad Sci U S A PMCID PMC9245612 PMID 35733246 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML