Cryo EM analyzed the detailed structure of angiotensin converting enzyme (ACE), a protein that helps regulate blood pressure. These structures provide the most comprehensive view of ACE so far and will help to improve the drug design of heart disease.
This work was completed by researchers from the University of Cape Town (UCT) in cooperation with the electronic biological imaging center (EBIC) of the British synchrotron radiation source”diamond”. The researchers published their findings in the EMBO Journal (“cryoelectron microscopy revealed the isomerization and dimerization mechanism of angiotensin I converting enzyme”).
Ace produces the hormone angiotensin II, which constricts blood vessels and raises blood pressure. Hypertension is a major risk factor for heart disease and stroke.
Compared with previous methods,Cryoelectron microscopy enables researchers to observe ace in more functionally relevant States.Their work provides key insights into their biological functions and potential drug binding properties.
A copy of ACE protein (i.e. monomer form) is connected by two domains with similar structure but different functions. Dimerization (i.e. the interaction of two ace monomers) occurs near a small surface cavity, changing the conformation of the core amino acids that are crucial to ace function.
Researchers suggest that this dimerization may act as a”turn off switch”, triggering changes in the protein core and possibly inhibiting it. If a drug like molecule can be designed to bind in the cavity and cause the same effect, it can provide a new means to inactivate the enzyme.
At present, many ACE inhibitors can be used to treat hypertension in clinic. However, these inhibitors non selectively target two ace domains, and thus cause side effects in some patients.
Dr. Edward Sturrock, a professor at the University of Cape Town and the principal investigator of the study, explained:
“It is important to understand the structure and dynamics of these newly discovered ace, which may provide new binding sites for the design of domain selective inhibitors to avoid side effects.”
Ace protein was produced in Sturrock’s laboratory, prepared before imaging in the electron microscope unit (EMU) of uct, and then transferred to EBIC for freeze electron microscope imaging on Titan Krios. Image processing is carried out at CSIR High Performance Computing Center (CHPC) and EMU in South Africa.”Even with high-resolution imaging, the unique shape, small molecular weight and high dynamics of ACE pose many challenges,” explained Dr. Jeremy Woodward, one of the co authors of the study.
Dr. lizelle Lubbe, the first author of the study, explained:
“The recently developed image processing method of freeze electron microscope is very important to analyze these structures.”
We must calculate the separation image through extensive classification, which is equivalent to ‘digital purification’, because biochemical methods cannot separate the monomer and dimer forms of ace. Then, we can focus on different parts of the structure in order to analyze these two ace structures.
The findings of this study uniquely reveal the highly dynamic characteristics of ACE and the mechanism of dimerization and communication between its different domains – which may inspire new drugs for the treatment of heart disease.
Dr Chris Nicklin, leader of diamond scientific team, said:
“We are pleased with the results of this study made by a team of outstanding scientists in Africa using EBIC’s advanced cryoelectron microscope. The world urgently needs sustainable solutions for fatal heart disease and other chronic health conditions. We are very pleased that the structural insights of this study can pave the way for improving the design of antihypertensive drugs.”
Cryo-EM Structures of a Key Hypertension Protein to Aid Drug Design
Cryo EM reveals the expression of angiotensin I converting enzymeMechanism of isomerization and dimerization
Hypertension (hypertension) is a major risk factor for cardiovascular disease, which is the leading cause of death worldwide. The somatic isomers of angiotensin I converting enzyme (SACE) play a key role in blood pressure regulation, so ACE inhibitors are widely used in the treatment of hypertension and cardiovascular diseases.
Our current understanding of the structure, dynamics, function and inhibition of SACE is limited, because the truncated, minimal glycosylated form of SACE is usually used for X-ray crystallography and molecular dynamics simulation. Here, we report for the first time the structure of the full-length, glycosylated, soluble SACE (saces1211) under the freeze electron microscope. The monomer and dimer forms of this highly flexible apo enzyme were reconstructed from a data set. The N-terminal and C-terminal structures of the monomer saces1211 were resolved at 3.7 and 4.1 Å, respectively, while the N-terminal structure responsible for the interaction of dimer formation was resolved at 3.8 Å. In addition, it is observed that both domains are in open conformation, which is of significance for the design of SACE regulators.
“Cryo-EM reveals mechanisms of angiotensin I-converting enzyme allostery and dimerization”