biostudies-literatureFranklin EHoward Hughes Medical InstituteDivision of Molecular and Cellular BiosciencesBill and Melinda Gates FoundationNational Institute of General Medical SciencesNIGMS NIH HHS359-372https://www.ebi.ac.uk/biostudies/studies/S-EPMC12676092biostudies-literatureUnknown249(1)Pyrenoids are algal CO₂-fixing organelles that mediate approximately one-third of global carbon fixation. Most pyrenoids are traversed by membranes that are thought to supply them with concentrated CO₂. Despite the critical nature of these membranes for pyrenoid function, they are poorly understood, with few protein components known in any species. Here, we identify protein components of the pyrenoid-traversing membranes from the leading model alga, Chlamydomonas reinhardtii, by affinity purification and mass spectrometry of membrane fragments. Our proteome includes previously known proteins as well as novel candidates. We further characterize two of the novel pyrenoid-traversing membrane-resident proteins: Cre10.g452250, which we name Pyrenoid Membrane Enriched 1 (PMThe New phytologistProteomic analysis of the pyrenoid-traversing membranes of Chlamydomonas reinhardtii reveals novel components.PMC12676092INV-054558MCB-19149891R01GM140032-01T32GM007388MCB-2410354MCB‐19149891R01GM140032‐01MCB‐2410354INV‐054558Pacini CLunardon AJonikas MCDuggal KFranklin EPatena WCruz ERErgun SLWang LGarde AfalseProteomic analysis of the pyrenoid-traversing membranes of Chlamydomonas reinhardtii reveals novel components.Pyrenoids are algal CO₂-fixing organelles that mediate approximately one-third of global carbon fixation. Most pyrenoids are traversed by membranes that are thought to supply them with concentrated CO₂. Despite the critical nature of these membranes for pyrenoid function, they are poorly understood, with few protein components known in any species. Here, we identify protein components of the pyrenoid-traversing membranes from the leading model alga, Chlamydomonas reinhardtii, by affinity purification and mass spectrometry of membrane fragments. Our proteome includes previously known proteins as well as novel candidates. We further characterize two of the novel pyrenoid-traversing membrane-resident proteins: Cre10.g452250, which we name Pyrenoid Membrane Enriched 1 (PM2026-01-01T00:00:00Z2026 Jan2026-06-05T22:07:50.554Z2026-05-22T03:16:09.164ZS-EPMC126760924111673510.1111/nph.70669