Premium
Structure and function of LCI1: a plasma membrane CO 2 channel in the Chlamydomonas CO 2 concentrating mechanism
Author(s) -
Kono Alfredo,
Chou TsungHan,
Radhakrishnan Abhijith,
Bolla Jani Reddy,
Sankar Kannan,
Shome Sayane,
Su ChihChia,
Jernigan Robert L.,
Robinson Carol V.,
Yu Edward W.,
Spalding Martin H.
Publication year - 2020
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.14745
Subject(s) - chlamydomonas reinhardtii , chlamydomonas , photosynthesis , membrane , biophysics , assimilation (phonology) , biology , aquaporin , cyanobacteria , carbon assimilation , microbiology and biotechnology , mutant , biochemistry , gene , genetics , bacteria , linguistics , philosophy
Microalgae and cyanobacteria contribute roughly half of the global photosynthetic carbon assimilation. Faced with limited access to CO 2 in aquatic environments, which can vary daily or hourly, these microorganisms have evolved use of an efficient CO 2 concentrating mechanism (CCM) to accumulate high internal concentrations of inorganic carbon (C i ) to maintain photosynthetic performance. For eukaryotic algae, a combination of molecular, genetic and physiological studies using the model organism Chlamydomonas reinhardtii , have revealed the function and molecular characteristics of many CCM components, including active C i uptake systems. Fundamental to eukaryotic C i uptake systems are C i transporters/channels located in membranes of various cell compartments, which together facilitate the movement of C i from the environment into the chloroplast, where primary CO 2 assimilation occurs. Two putative plasma membrane C i transporters, HLA3 and LCI1, are reportedly involved in active C i uptake. Based on previous studies, HLA3 clearly plays a meaningful role in HCO 3 − transport, but the function of LCI1 has not yet been thoroughly investigated so remains somewhat obscure. Here we report a crystal structure of the full‐length LCI1 membrane protein to reveal LCI1 structural characteristics, as well as in vivo physiological studies in an LCI1 loss‐of‐function mutant to reveal the C i species preference for LCI1. Together, these new studies demonstrate LCI1 plays an important role in active CO 2 uptake and that LCI1 likely functions as a plasma membrane CO 2 channel, possibly a gated channel.