Bacillus subtilis YisK possesses oxaloacetate decarboxylase activity and exhibits Mbl-dependent localization

YisK is an uncharacterized protein in Bacillus subtilis previously shown to interact genetically with the elongasome protein Mbl. YisK overexpression leads to cell widening and lysis, phenotypes that are dependent on mbl and suppressed by mbl mutations. In the present work we characterize YisKs localization, structure, and enzymatic activity. We show that YisK localizes in a punctate and/or punctate-helical pattern that depends on Mbl, and that YisK interacts directly with another elongasome protein, FtsE. YisK belongs to the fumarylacetoacetate hydrolase (FAH) superfamily and crystal structures revealed close structural similarity to two oxaloacetate (OAA) decarboxylases: human mitochondrial FAHD1 and Corynebacterium glutamicum Cg1458. We demonstrate that YisK can also catalyze the decarboxylation of OAA (Km = 134 {micro}M, Kcat = 31 min-1). A catalytic dead variant (YisK E148A, E150A) retains wild-type localization and still widens cells following overexpression, indicating these activities are not dependent on YisK catalysis. Conversely, a non-localizing variant (YisK E30A) retains wild-type enzymatic activity in vitro, but no longer widens cells following overexpression. Together these results suggest YisK may be subject to spatial regulation that depends on the cell envelope synthesis machinery. IMPORTANCEThe elongasome is a protein complex that guides lengthwise growth in some bacteria. We previously showed that in B. subtilis, overexpression of an uncharacterized enzyme (YisK), perturbed function of the actin-like elongasome protein Mbl. Here we show that YisK exhibits Mbl-dependent localization and interacts directly with another component of the elongasome, FtsE. Through biochemical and structural characterization, we demonstrate that like its mitochondrial homolog FAHD1, YisK can catalyze the decarboxylation of the oxaloacetate to pyruvate and CO2. YisK is the first example of an enzyme implicated in central carbon metabolism with subcellular localization that depends on Mbl.