Cholesterol binding is a prerequisite for the activity of the steroidogenic acute regulatory protein (StAR)

2008 ◽  
Vol 412 (3) ◽  
pp. 553-562 ◽  
Author(s):  
Alireza Roostaee ◽  
Élie Barbar ◽  
Jean-Guy LeHoux ◽  
Pierre Lavigne
Keyword(s):  
Thermodynamic Stability ◽  
Tertiary Structure ◽  
Regulatory Protein ◽  
Biologically Active ◽  
Steroidogenic Acute Regulatory Protein ◽  
Proper Function ◽  
Stable Complex ◽  
Steroidogenic Acute Regulatory ◽  
Α Helix ◽  
Cholesterol Binding

Steroidogenesis depends on the delivery of cholesterol from the outer to the inner mitochondrial membrane by StAR (steroidogenic acute regulatory protein). However, the mechanism by which StAR binds to cholesterol and its importance in cholesterol transport are under debate. According to our proposed molecular model, StAR possesses a hydrophobic cavity, which can accommodate one cholesterol molecule. In the bound form, cholesterol interacts with hydrophobic side-chains located in the C-terminal α-helix 4, thereby favouring the folding of this helix. To verify this model experimentally, we have characterized the in vitro activity, overall structure, thermodynamic stability and cholesterol-binding affinity of StAR lacking the N-terminal 62 amino acid residues (termed N-62 StAR). This mature form is biologically active and has a well-defined tertiary structure. Addition of cholesterol to N-62 StAR led to an increase in the α-helical content and T° (melting temperature), indicating the formation of a stable complex. However, the mutation F267Q, which is located in the C-terminal helix interface lining the cholesterol-binding site, reduced the biological activity of StAR. Furthermore, the cholesterol-induced thermodynamic stability and the binding capacity of StAR were significantly diminished in the F267Q mutant. Titration of StAR with cholesterol yielded a 1:1 complex with an apparent KD of 3×10−8. These results support our model and indicate that StAR can readily bind to cholesterol with an apparent affinity that commensurates with monomeric cholesterol solubility in water. The proper function of the C-terminal α-helix is essential for the binding process.

The mechanism of specific binding of free cholesterol by the steroidogenic acute regulatory protein: evidence for a role of the C-terminal α-helix in the gating of the binding site

2009 ◽  
Vol 29 (2) ◽  
pp. 89-101 ◽  
Author(s):  
Alireza Roostaee ◽  
Élie Barbar ◽  
Pierre Lavigne ◽  
Jean-Guy Lehoux
Keyword(s):  
Binding Site ◽  
Free Cholesterol ◽  
Specific Binding ◽  
Regulatory Protein ◽  
Salt Bridge ◽  
Steroidogenic Acute Regulatory Protein ◽  
Steroidogenic Acute Regulatory ◽  
Α Helix ◽  
The Impact ◽  
Cholesterol Binding

Steroidogenesis depends on the delivery of free cholesterol to the inner mitochondrial membrane by StAR (steroidogenic acute regulatory protein). Mutations in the StAR gene leads to proteins with limited cholesterol-binding capacity. This gives rise to the accumulation of cytoplasmic cholesterol, a deficit in steroid hormone production and to the medical condition of lipoid congenital adrenal hyperplasia. A detailed understanding of the mechanism of the specific binding of free cholesterol by StAR would be a critical asset in understanding the molecular origin of this disease. Previous studies have led to the proposal that the C-terminal α-helix 4 of StAR was undergoing a folding/unfolding transition. This transition is thought to gate the cholesterol-binding site. Moreover, a conserved salt bridge (Glu169–Arg188) in the cholesterol-binding site is also proposed to be critical to the binding process. Interestingly, some of the documented clinical mutations occur at this salt bridge (E169G, E169K and R188C) and in the C-terminal α-helix 4 (L275P). In the present study, using rationalized mutagenesis, activity assays, CD, thermodynamic studies and molecular modelling, we characterized the α-helix 4 mutations L271N and L275P, as well as the salt bridge double mutant E169M/R188M. The results provide experimental validation for the gating mechanism of the cholesterol-binding site by the C-terminal α-helix and the importance of the salt bridge in the binding mechanism. Altogether, our results offer a molecular framework for understanding the impact of clinical mutations on the reduction of the binding affinity of StAR for free cholesterol.

scholarly journals The Steroidogenic Acute Regulatory Protein Homolog MLN64, a Late Endosomal Cholesterol-binding Protein

2000 ◽  
Vol 276 (6) ◽  
pp. 4261-4269 ◽  
Author(s):  
Fabien Alpy ◽  
Marie-Elisabeth Stoeckel ◽  
Andrée Dierich ◽  
Jean-Michel Escola ◽  
Corinne Wendling ◽  
...  
Keyword(s):  
Binding Protein ◽  
Regulatory Protein ◽  
Steroidogenic Acute Regulatory Protein ◽  
Steroidogenic Acute Regulatory ◽  
Cholesterol Binding

Evolutionary Analysis of the Steroidogenic Acute Regulatory Protein-Related Lipid Transfer Domain and Its Response to Salt Stress In Vitis Vinifera

2021 ◽  
Author(s):  
Honghong He ◽  
Huiming Gou ◽  
Qi Zhou ◽  
Xuejing Cao ◽  
Ping Wang ◽  
...  
Keyword(s):  
Salt Stress ◽  
Vitis Vinifera ◽  
Gene Family ◽  
Tertiary Structure ◽  
Expression Profiles ◽  
Regulatory Protein ◽  
Steroidogenic Acute Regulatory Protein ◽  
Evolutionary Analysis ◽  
Lipid Transfer ◽  
Steroidogenic Acute Regulatory

Abstract This study aimed to enhance the understanding of the steroidogenic acute regulatory protein-related lipid transfer (START) domain in Vitis vinifera. A total of 23 members of the VvSTARD gene family were found, which could be divided into five groups. The analyses of the gene codon preference, selective pressure, and tandem replication events of the VvSTARD, AtSTARD, and OsSTARD genomes indicated that tandem replication events occured in grapes, Arabidopsis, and rice genomes. Eight lipid transporter proteins were found in the tertiary structure of the STARD gene family in grapes. The analysis of the expression profiles of the three species microarrays showed that the expression sites of the STARD gene and the response to abiotic stress in the same subgroup had similar characteristics. In addition, quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze the expression of the STARD gene family in grape leaves in response to different hormones and abiotic stresses, and the obtained results were the same as those predicted by the cis-elements and the expression profiles. Furthermore, 35S:STARD5:EGFP was successfully constructed to verify the subcellular prediction results, and the results showed that STARD5 was located in the nucleus. Through the identification of salt tolerance of transgenic tomato, STARD5 was found to regulate the salt stress of plants. Collectively, these data indicated that the VvSTARD gene family plays an important role in response to salt stress.

scholarly journals Insights into steroidogenic acute regulatory protein (StAR)-dependent cholesterol transfer in mitochondria: evidence from molecular modeling and structure-based thermodynamics supporting the existence of partially unfolded states of StAR

2002 ◽  
Vol 29 (3) ◽  
pp. 327-345 ◽  
Author(s):  
AP Mathieu ◽  
A Fleury ◽  
L Ducharme ◽  
P Lavigne ◽  
JG LeHoux
Keyword(s):  
Molecular Structure ◽  
Binding Site ◽  
Regulatory Protein ◽  
Steroidogenic Acute Regulatory Protein ◽  
Star Activity ◽  
Charged Pair ◽  
Steroidogenic Acute Regulatory ◽  
Partially Unfolded ◽  
Partially Unfolded States ◽  
Cholesterol Binding

The steroidogenic acute regulatory protein (StAR) is the major entrance for cholesterol in mitochondria under acute stimulation. Under such circumstances, dysfunctional StAR activity can ultimately lead to lipoid congenital adrenal hyperplasia (LCAH). A complete understanding of the StAR's molecular structure and mechanism is essential to comprehend LCAH. Thus far, there is no mechanistic model that can explain experimental results at the molecular level. This is partly due to the lack of the molecular structure of StAR. The closest approximation to the StAR molecular structure is the human MLN64 which has a similar activity to StAR, has a highly homologous primary structure and for which an X-ray structure is known. In this context, we have modeled the structure of StAR through standard homology modeling procedures based on the MLN64 structure. Our StAR model shows the presence of a hydrophobic cavity of 783.9 A(2) in surface area, large enough to fit one molecule of cholesterol. In addition, we have identified a unique charged pair, as in MLN64, lining the surface of the cavity and which could play a key role in the binding of cholesterol through the formation of an H-bond with its OH moiety. This suggests that the cholesterol-binding site of StAR is located inside this cavity. Taking into account that internal cavities are destabilizing to native protein structures and that the lining of the cavity has to become accessible in order to allow cholesterol binding, we have explored the possibility that StAR could exist in equilibrium with partially unfolded states. Using a structure-based thermodynamics approach, we show that partially folded states (with an unfolded C-terminal alpha-helix, and an open cavity) can be significantly populated at equilibrium and therefore allow cholesterol binding. These results are supported by recent experiments that show a loss of StAR helical character upon binding of an analog of cholesterol. Moreover, we show that the replacement of the residues involved in the charged-pair located in the binding site results in the loss of StAR activity, supporting a key role for these residues. Taken together, our results are applicable to StAR functioning both in the mitochondrial intermembrane space as well as outside the mitochondria.

Molten-globule structure and membrane binding of the N-terminal protease-resistant domain (63–193) of the steroidogenic acute regulatory protein (StAR)

2001 ◽  
Vol 356 (1) ◽  
pp. 151-158
Author(s):  
Maengseok SONG ◽  
Haiyan SHAO ◽  
Anwer MUJEEB ◽  
Thomas L. JAMES ◽  
Walter L. MILLER
Keyword(s):  
Secondary Structure ◽  
Tertiary Structure ◽  
Molten Globule ◽  
Regulatory Protein ◽  
Limited Proteolysis ◽  
Proteinase K ◽  
Steroidogenic Acute Regulatory Protein ◽  
Inner Mitochondrial Membrane ◽  
Terminal Domain ◽  
Steroidogenic Acute Regulatory

The first step in steroidogenesis is the movement of cholesterol from the outer to inner mitochondrial membrane; this movement is facilitated by the steroidogenic acute regulatory protein (StAR). StAR has molten-globule properties at low pH and a protease-resistant N-terminal domain at pH4 and pH8 comprising residues 63–193. To explore the mechanism of action of StAR we investigated the structural properties of the bacterially expressed N-terminal domain (63–193 StAR) using CD, limited proteolysis and NMR. Far- and near-UV CD showed that the amount of secondary structure was greater at acidic than at neutral pH, but there was little tertiary structure at any pH. Unlike 63–193 StAR liberated from N-62 StAR by proteolysis, biosynthetic 63–193 StAR was no longer resistant to trypsin or proteinase K at pH7, or to pepsin at pH4. Addition of trifluoroethanol and SDS increased secondary structure at pH7, and dodecylphosphocholine and CHAPS increased secondary structure at pH2, pH4 and pH7. However, none of these conditions induced tertiary structure, as monitored by near-UV CD or NMR. Liposomes of phosphatidylcholine, phosphatidylserine and their mixture increased secondary structure of 63–193 StAR at pH7, as monitored by far-UV CD, and stable protein–liposome complexes were identified by gel-permeation chromatography. These results provide further evidence that the N-terminal domain of StAR is a molten globule, and provide evidence that this conformation facilitates the interaction of the N-terminal domain of StAR with membranes. We suggest that this interaction is the key to understanding the mechanism of StAR's action.

Von Hermaphroditos der griechischen Mythologie bis zu DSD der Moderne

Praxis ◽  
2008 ◽  
Vol 98 (1) ◽  
pp. 31-34
Author(s):  
Oestmann ◽  
Mullis ◽  
Stanga
Keyword(s):  
Regulatory Protein ◽  
Steroidogenic Acute Regulatory Protein ◽  
Sich Eine ◽  
Fand Sich ◽  
Steroidogenic Acute Regulatory

Wir berichten über eine heute 34-jährige Frau, die im Alter von 6 Monaten wegen rezidivierendem Erbrechen hospitalisiert werden musste. Als Ursache fand sich eine Nebenniereninsuffizienz mit Verminderung sämtlicher Hormone der Steroidhormonbiosynthese. Die weiteren Abklärungen ergaben bei dem phänotypisch weiblichen Säugling eine lipoide kongenitale adrenale Hyperplasie mit 46,XY DSD. 24 Jahre später konnte in der DNS-Sequenzanalyse ein homozygoter, in der Schweiz vorkommender Basenaustausch des steroidogenic acute regulatory protein-Gens gefunden werden, welcher zu einem Aminosäurenaustausch Leucin 260 Prolin (L260P) führt.

2040-P: Chronic Activation of CREB by Islet Amyloid Increases Star (Steroidogenic Acute Regulatory Protein) Expression in Islets

Diabetes ◽  
2020 ◽  
Vol 69 (Supplement 1) ◽  
pp. 2040-P
Author(s):  
MEGHAN F. HOGAN ◽  
NATHALIE ESSER ◽  
ANDREW T. TEMPLIN ◽  
JOSEPH J. CASTILLO ◽  
SAKENEH ZRAIKA ◽  
...  
Keyword(s):  
Protein Expression ◽  
Regulatory Protein ◽  
Steroidogenic Acute Regulatory Protein ◽  
Islet Amyloid ◽  
Chronic Activation ◽  
Steroidogenic Acute Regulatory
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