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Publication Abstract from PubMed

Halorhodospira (Hlr.) halophila strain BN9622 is an extremely halophilic and alkaliphilic phototrophic purple sulfur bacterium isolated from a hypersaline lake in the Libyan Desert whose total salinity exceeded 35% at pH 10.7. Here we present a cryo-EM structure of the native LH1-LH2 co-complex from strain BN9622 at 2.22 A resolution. Surprisingly, the LH1-LH2 co-complex consists of a double-ring cylindrical structure with the larger LH1 ring encircling a smaller LH2 ring. The Hlr. halophila LH1 contains 18 alphabeta-subunits and additional bacteriochlorophyll a (BChl a) molecules that absorb maximally at 797 nm. The LH2 ring is composed of 9 alphabeta-subunits, and the BChl a molecules in the co-complex form extensive intra- and inter-complex networks to allow near 100% efficiency of energy transfer to its surrounding LH1. The additional LH1-B797 BChls a are located in such a manner that they facilitate exciton transfer from monomeric BChls in LH2 to the dimeric BChls in LH1. The structural features of the strain BN9622 LH1-LH2 co-complex may have evolved to allow a minimal LH2 complex to maximize excitation transfer to the core complex and effectively harvest light in the physiologically demanding ecological niche of this purple bacterium.

A distinct double-ring LH1-LH2 photocomplex from an extremophilic phototroph.,Tani K, Nagashima KVP, Kojima R, Kondo M, Kanno R, Satoh I, Kawakami M, Hiwatashi N, Nakata K, Nagashima S, Inoue K, Isawa Y, Morishita R, Takaichi S, Purba ER, Hall M, Yu LJ, Madigan MT, Mizoguchi A, Humbel BM, Kimura Y, Nagasawa Y, Dewa T, Wang-Otomo ZY Nat Commun. 2025 Feb 6;16(1):1410. doi: 10.1038/s41467-024-55811-9. PMID:39915441^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.