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Sorghum bicolor membrane steroid binding protein 1 can bind heme and remodel ER membranes

Ratanasopa, Khuanpiroon LU ; Ochoa-Fernandez, Rocio ; Mellor, Silas B. ; Travaglia, Valentina ; Hinz, Kasper ; Tuelung, Pernille S. and Laursen, Tomas (2026) In Plant and Cell Physiology 67(3). p.315-328
Abstract

Plant membrane steroid binding proteins (MSBPs) belong to the membrane-associated progesterone receptors (MAPRs), which is present in all eukaryotic kingdoms. Plant MSBPs have been shown to regulate the function of cytochrome P450 enzymes, bind different steroidal compounds and confer salt tolerance. However, the exact molecular function of plant MSBPs remains elusive. Here, we perform a phylogenetic analysis of the six MAPR genes encoded in the Sorghum bicolor genome. Of these, four group into a distinct MSBP clade characterized by being N-terminally membrane anchored followed by a cytochrome b5 domain and an extended disordered C-terminal. Biophysical characterization of SbMSBP1 demonstrates that this protein can bind heme,... (More)

Plant membrane steroid binding proteins (MSBPs) belong to the membrane-associated progesterone receptors (MAPRs), which is present in all eukaryotic kingdoms. Plant MSBPs have been shown to regulate the function of cytochrome P450 enzymes, bind different steroidal compounds and confer salt tolerance. However, the exact molecular function of plant MSBPs remains elusive. Here, we perform a phylogenetic analysis of the six MAPR genes encoded in the Sorghum bicolor genome. Of these, four group into a distinct MSBP clade characterized by being N-terminally membrane anchored followed by a cytochrome b5 domain and an extended disordered C-terminal. Biophysical characterization of SbMSBP1 demonstrates that this protein can bind heme, which leads to dimerization potentially through a heme–heme stacking mechanism. Using untargeted proteomics, We further show that MSBPs are upregulated in both root and shoot tissues upon exposure to salt stress. Based on weighted gene co-expression network analysis, we find that SbMSBP1 abundance clusters with endoplasmic reticulum (ER) remodeling and vesicle transport proteins. We further show that overexpression of SbMSBP1 in S. bicolor protoplasts and tobacco results in formation of structures consistent with organized smooth ER. Our data indicate that SbMSBP1 functions to remodel ER membranes, which may be directly linked to a functional role in stress resilience toward both biotic and abiotic stresses and furthermore could serve as a useful tool for metabolic engineering of ER-scaffolded biosynthetic pathways.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ER membrane dynamics, membrane steroid binding protein, organized smooth endoplasmic reticulum, salt stress, Sorghum bicolor, vesicle transport
in
Plant and Cell Physiology
volume
67
issue
3
pages
14 pages
publisher
Oxford University Press
external identifiers
  • pmid:41342392
  • scopus:105036401498
ISSN
0032-0781
DOI
10.1093/pcp/pcaf160
language
English
LU publication?
yes
additional info
Publisher Copyright: © The Author(s) 2025. Published by Oxford University Press on behalf of the Japanese Society of Plant Physiologists.
id
45bf75d1-393b-4d4e-b6f4-eaeadddf3a04
date added to LUP
2026-05-06 07:20:53
date last changed
2026-06-17 10:33:23
@article{45bf75d1-393b-4d4e-b6f4-eaeadddf3a04,
  abstract     = {{<p>Plant membrane steroid binding proteins (MSBPs) belong to the membrane-associated progesterone receptors (MAPRs), which is present in all eukaryotic kingdoms. Plant MSBPs have been shown to regulate the function of cytochrome P450 enzymes, bind different steroidal compounds and confer salt tolerance. However, the exact molecular function of plant MSBPs remains elusive. Here, we perform a phylogenetic analysis of the six MAPR genes encoded in the Sorghum bicolor genome. Of these, four group into a distinct MSBP clade characterized by being N-terminally membrane anchored followed by a cytochrome b<sub>5</sub> domain and an extended disordered C-terminal. Biophysical characterization of SbMSBP1 demonstrates that this protein can bind heme, which leads to dimerization potentially through a heme–heme stacking mechanism. Using untargeted proteomics, We further show that MSBPs are upregulated in both root and shoot tissues upon exposure to salt stress. Based on weighted gene co-expression network analysis, we find that SbMSBP1 abundance clusters with endoplasmic reticulum (ER) remodeling and vesicle transport proteins. We further show that overexpression of SbMSBP1 in S. bicolor protoplasts and tobacco results in formation of structures consistent with organized smooth ER. Our data indicate that SbMSBP1 functions to remodel ER membranes, which may be directly linked to a functional role in stress resilience toward both biotic and abiotic stresses and furthermore could serve as a useful tool for metabolic engineering of ER-scaffolded biosynthetic pathways.</p>}},
  author       = {{Ratanasopa, Khuanpiroon and Ochoa-Fernandez, Rocio and Mellor, Silas B. and Travaglia, Valentina and Hinz, Kasper and Tuelung, Pernille S. and Laursen, Tomas}},
  issn         = {{0032-0781}},
  keywords     = {{ER membrane dynamics; membrane steroid binding protein; organized smooth endoplasmic reticulum; salt stress; Sorghum bicolor; vesicle transport}},
  language     = {{eng}},
  number       = {{3}},
  pages        = {{315--328}},
  publisher    = {{Oxford University Press}},
  series       = {{Plant and Cell Physiology}},
  title        = {{Sorghum bicolor membrane steroid binding protein 1 can bind heme and remodel ER membranes}},
  url          = {{http://dx.doi.org/10.1093/pcp/pcaf160}},
  doi          = {{10.1093/pcp/pcaf160}},
  volume       = {{67}},
  year         = {{2026}},
}