Crystal Structure of 4-Hydroxybutyryl-CoA Synthetase (ADP-forming): A Key Enzyme in the Thaumarchaeal Hydroxypropionate/Hydroxybutyrate cycle

Abstract

The 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) cycle from ammonia-oxidizing Thaumarchaeota is currently considered the most energy-efficient aerobic carbon fixation pathway. The Nitrosopumilus maritimus 4-hydroxybutyryl-CoA synthetase (ADP-forming) (Nmar_0206) from this cycle represents one of a number of proteins that exhibit increased efficiency over its crenarchaeal counterparts. Nmar_0206 catalyzes the conversion of 4-hydroxybutyrate (4HB) and Coenzyme-A (CoA) to 4-hydroxybutyryl-CoA through the dephosphorylation of ATP to ADP, as opposed to AMP as seen in Crenarchaeota. This enzyme reduces energy requirements on the cell, thus reflecting thaumarchaeal success in adapting to low-nutrient environments.