Sulfate assimilation in L. hongkongensis HLHK9. (A) Sulfate assimilation pathways in bacteria. Two pathways exist in bacteria which differ in the form of sulfate being activated. In one pathway that was once assumed to be the only one, APS is converted to PAPS by APS kinase and subsequently reduced to sulfite by PAPS reductase (green arrow). In the other pathway, APS is directly reduced to sulfite by APS reductase (orange arrow). Homologues of genes found in L. hongkongensis HLHK9 were specified with gene numbers in blue. APS, adenosine 5'-adenylylsulfate; PAPS, 3'-phosphoadenylylsulfate. (B) Multiple sequence alignment of predicted APS reductase in L. hongkongensis with other characterized or related bacterial APS and PAPS reductases. Characterized APS reductases include those from Burkholderia cepacia, Arabidopsis thaliana, Rhizobium meliloti whereas characterized PAPS reductases include the one from E. coli. Only the selected region which contains two-cysteine motifs, CCXXRKXXPL and SXGCXXCT, in the C-terminal of APS reductase is shown. The conserved cysteine residues are shaded in yellow. The sequences were aligned with ClustalW. The abbreviations used and accession numbers (shown in parentheses) are as follows: At, A. thaliana (GenBank:NP_193930); Bc, B. cenocepacia J2315 [GenBank:YP_002231786]; Cv, C. violaceum ATCC 12472 [GenBank:NP_903244]; Ec, E. coli K-12 MG1655, [GenBank:NP_417242]; Lh, L. hongkongensis HLHK9 [GenBank:YP_002794611]; Nm, N. meningitidis MC58, [GenBank:NP_274183]; Se, Salmonella enterica subsp. enterica serovar Newport str. SL317 [GenBank:ZP_02697826]; Sp, Shewenella putrefaciens 200 [GenBank:ZP_01705880]; Sm, Rhizobium (Sinorhizobium meliloti 1021) [GenBank:NP_385050] and Vc, Vibrio cholera TM 11079-80 [GenBank:ZP_04409338].