The proteins required for catabolism of glycerol 3- phosphate are encoded by the genes of the <i>glp</i> regulon of Escherichia coli and are under negative transcriptional regulation by the <i>glpR</i>-encoded repressor. The <i>glpR</i> gene is adjacent to, and is transcribed divergently from, <i>glpD</i>. <i>GlpR</i> and <i>glpD</i> are separated by two open reading frames, designated <i>glpE</i> and <i>glpG</i>, encoding proteins of unknown function. The <i>glpD</i>-encoded aerobic sn-glycerol 3-phosphate dehydrogenase is a cytosplasmic membrane-associated respiratory enzyme. The nucleotide sequence of <i>glpD</i> was determined. An open reading frame of 501 codons was preceded by a consensus Shine-Dalgarno sequence. The proposed translational start and reading frame of glpD were confirmed by determining the nucleotide sequence across the fusion joint of a <i>glpD-lacZ</i>- translational fusion. / Ph. D.