Angiotensin-converting enzyme 2 (ACE2, also known as ACEH) is a transmembrane protein, which acts as receptor for SARS-CoV, SARS-CoV-2, and other coronaviruses. The large extracellular peptidase domain of ACE2 is known to interact with the spike protein of coronaviruses. The small C-terminal collectrin-like domain (CLD) has recently been described to mediate homo-dimerization of ACE2.  

We offer Recombinant Human ACE2 produced in HEK cells including C-terminal CLD or insect cell–derived ACE2 lacking CLD. The potential influence of the CLD domain is indicated by the exemplary analysis below. 
 

The surface or spike (S) glycoprotein plays a critical role in coronavirus infection as it is crucial for recognition and fusion of the virus with the host cell membrane. Two different functional domains of the S protein are responsible for these individual processes: The S1 domain contains the receptor binding domain, which binds to the host cell receptor ACE2, whereas membrane fusion is mediated via the S2 domain. Furthermore, cleavage at the furin cleavage site at the boundary of the S1 and S2 domains (aa residues 682 and 685) via cellular proteases primes the protein for entry into the host cell. Upon fusion of the viral envelope to the host cell membrane, the viral genome enters the host cell and viral replication starts.

Spike trimer

In its active form, the spike protein is displayed as a homotrimeric structure on the surface of the SARS-CoV-2 virus. 

We offer the recombinant SARS-CoV-2 spike trimer produced in HEK cells:  

Our Recombinant SARS-CoV-2 Spike-Trimer (HEK) covers the ectodomain of the viral surface protein, including the S1 and S2 domain (aa V16 to K1211). The recombinant protein contains stabilizing proline substitutions at position K986P and V987P as well as a mutated furin cleavage site (RRAR to GSAG substitution at residues 682–685). A T4 fibritin trimerization motif induces the conformation of a highly stable native-like homotrimer. 
 

Spike monomer

In vivo, three spike monomers form a homotrimeric structure on the surface of the SARS-CoV-2 virus; however, only one monomer appears to interact with the host cell receptor.  

We offer the recombinant SARS-CoV-2 spike monomer produced in HEK cells:  

Our Recombinant SARS-CoV-2 Spike-Prot (HEK) covers the ectodomain of the viral surface protein, including the S1 and S2 domain (aa V16 to K1211). The recombinant protein contains stabilizing proline substitutions at position K986P and V987P as well as a mutated furin cleavage site (RRAR to GSAG substitution at residues 682–685).  
 

Furin cleavage site (and control) 

The junction connecting the S1 and S2 domain of the spike protein contains a furin cleavage site at position R682–R685 (RRAR). Recent structural studies on the SARS-CoV-2 spike protein showed that this part of the protein is solvent-exposed and disordered.   

We offer synthesized polypeptides as antigens for the furin cleavage site and a control with a mutated furin cleavage site (RRAR to GSAG substitution).
  

Receptor binding domain

The receptor binding domain (RBD) locates C-terminally within the S1 subunit of the S protein. The S protein forms a homotrimeric structure on the surface of the SARS-CoV-2 virus. Recent studies have shown that the predominant activated form of the protein S trimer displays one RBD rotated up into an ACE2-accessible state. Binding of RBD to ACE2 is a major contributor for interaction of protein S with its target receptor.

We offer recombinant SARS-CoV-2 RBD produced in HEK or insect cells:
 

S1 domain 

The S1 domain is localized at the N-terminus of the spike protein. This subunit is crucial for virus–host cell interaction as it contains the receptor binding domain (RBD), which recognizes and binds  the host cell target receptor ACE2.    

We offer recombinant SARS-CoV-2 spike S1 produced in HEK cells:   
 

S2 domain 

The S2 domain is localized at the C-terminus of the spike protein and mediates membrane penetration as well as virus-to-cell fusion through the presence of so-called heptad repeats.   

We offer recombinant SARS-CoV-2 spike S2 produced in insect cells:  

Our SARS-CoV-2 Spike-S2 covers amino acids S686 to K1211 and contains stabilizing proline substitutions at position K986P and V987P. 
 

The SARS-CoV-2 nucleoprotein (also known as nucleocapsid protein or protein N) is a key structural protein of the SARS-CoV-2 virus. The N-terminal RNA-binding domain (NTD) associates with the viral genome of SARS-CoV-2. An intrinsically disordered stretch connects the NTD domain with the C-terminal dimerization domain (CTD). A major function of protein N is the packaging of the viral genome into helical nucleocapsid structures. Additionally, it is involved in virus transcription and interacts with the viral membrane during virion assembly. 

We offer recombinant SARS-CoV-2 nucleoprotein (full length):
 

The envelope protein (also known as envelope small membrane protein) is localized on the surface of the virus and represents one of the most relevant structural proteins of SARS-CoV-2. It acts as a viroporin and is involved in virus morphogenesis, assembly, and pathogenesis. Based on previous structural studies of highly similar envelope proteins from other coronaviruses and homology studies, it is assumed that the envelope protein forms a pentameric structure when integrated into the membrane of SARS-CoV-2. 

We offer synthesized polypeptides for three parts of the envelope protein: C- terminus, N-terminus, and helical segment 2 (H2).