Structures of maintenance of carboxysome distribution Walker-box McdA and McdB adaptor homologs.

Journal Article (Journal Article)

Carboxysomes, protein-coated organelles in cyanobacteria, are important in global carbon fixation. However, these organelles are present at low copy in each cell and hence must be segregated to ensure transmission from one generation to the next. Recent studies revealed that a DNA partition-like ParA-ParB system mediates carboxysome maintenance, called McdA-McdB. Here, we describe the first McdA and McdB homolog structures. McdA is similar to partition ParA Walker-box proteins, but lacks the P-loop signature lysine involved in ATP binding. Strikingly, a McdA-ATP structure shows that a lysine distant from the P-loop and conserved in McdA homologs, enables ATP-dependent nucleotide sandwich dimer formation. Similar to partition ParA proteins this ATP-bound form binds nonspecific-DNA. McdB, which we show directly binds McdA, harbors a unique fold and appears to form higher-order oligomers like partition ParB proteins. Thus, our data reveal a new signature motif that enables McdA dimer formation and indicates that, similar to DNA segregation, carboxysome maintenance systems employ Walker-box proteins as DNA-binding motors while McdB proteins form higher order oligomers, which could function as adaptors to link carboxysomes and provide for stable transport by the McdA proteins.

Full Text

Duke Authors

Cited Authors

  • Schumacher, MA; Henderson, M; Zhang, H

Published Date

  • June 20, 2019

Published In

Volume / Issue

  • 47 / 11

Start / End Page

  • 5950 - 5962

PubMed ID

  • 31106331

Pubmed Central ID

  • PMC6582323

Electronic International Standard Serial Number (EISSN)

  • 1362-4962

Digital Object Identifier (DOI)

  • 10.1093/nar/gkz314


  • eng

Conference Location

  • England