biostudies-literatureUnknown123(7)Arnold MFFSome legumes encode families of NCR (Nodule-Cysteine-Rich) peptides that cause their rhizobial partners to terminally differentiate during the development of a nitrogen-fixing symbiosis. <i>Sinorhizobium meliloti,</i> whose plant hosts <i>Medicago truncatula</i> and <i>Medicago sativa</i> express <i>ca.</i> 600 NCR peptides during root nodule development, possesses a symbiotically essential BacA<i>_Sm</i> protein that imports certain NCR peptides into the cytoplasm. This import permits proteolytic degradation of the NCR peptides, thereby protecting the endocytosed bacteria from their antimicrobial peptide-like lethality, while also allowing certain NCR peptides to undergo their symbiotically critical interactions with cytoplasmic components, for example heme-sequestration in the Proceedings of the National Academy of Sciences of the United States of Americae2526811123https://www.ebi.ac.uk/biostudies/studies/S-EPMC12912959biostudies-literatureBacA(SbmA) importer of legume symbiotic NCR peptides: Protein architecture, function, and evolutionary implications.PMC12912959Sankari SGruber CCGuerra-Garcia FJArnold MFFDeutsch MBeis KWalker GCfalseBacA(SbmA) importer of legume symbiotic NCR peptides: Protein architecture, function, and evolutionary implications.Some legumes encode families of NCR (Nodule-Cysteine-Rich) peptides that cause their rhizobial partners to terminally differentiate during the development of a nitrogen-fixing symbiosis. <i>Sinorhizobium meliloti,</i> whose plant hosts <i>Medicago truncatula</i> and <i>Medicago sativa</i> express <i>ca.</i> 600 NCR peptides during root nodule development, possesses a symbiotically essential BacA<i>_Sm</i> protein that imports certain NCR peptides into the cytoplasm. This import permits proteolytic degradation of the NCR peptides, thereby protecting the endocytosed bacteria from their antimicrobial peptide-like lethality, while also allowing certain NCR peptides to undergo their symbiotically critical interactions with cytoplasmic components, for example heme-sequestration in the 2026-01-01T00:00:00Z2026 Feb2026-07-16T06:50:14.081Z2026-07-09T10:41:02.838ZS-EPMC129129594166599710.1073/pnas.2526811123