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RC-100 retrocyclin

Pi Proteomics LLC is proud to be the exclusive distributor of the RC-100 retrocyclin peptide.  Retrocyclins 1 and 2 (also called RC-100 and RC100b) are novel circular peptides discovered by UCLA Researchers. Although they are produced synthetically, their structures are based on nucleotide sequences found in the human genome and/or in mRNA expressed by human bone marrow. Since human theta-defensin genes and retrocyclin bone marrow mRNA contain a premature stop codon in their signal sequence, retrocyclin peptides are probably not produced in humans. However, these peptides are found in certain Old World monkeys, and intact theta defensin genes are also present in lesser apes and orangutans (unpublished). Although the ability of theta defensins to kill bacteria is relatively modest, retrocyclin 1 and especially retrocyclin-2 show impressive activity against three different viral pathogens: human immunodeficiency virus (HIV-1), herpes simplex virus-1 and herpes simplex virus-2 (HSV-2). Although such broad specificity is somewhat reminiscent of interferons, retrocyclins operate as entry inhibitors. Retrocyclin-2 showed activity against a wide library of primary HIV-1 isolates of diverse subtypes, including subtypes A, B, C, CRF01, D, G, and recombinant subtypes. Its effectiveness was not dependent on or restricted by co-receptor (R5, X4 or R5X4) usage.

Potential Applications

Retrocyclins and other theta-defensins have been synthesized and shown to protect various CD4+ human cells from infection by HIV-1 in vitro. Retrocyclin-2, shows strong activity against laboratory-adapted strains of HIV-1, including IIIB (T cell tropic) and JR-CSF (M-tropic). It is also active against primary HIV-1 isolates representing subtypes A, B, C, CRF01, D, G, and various recombinant subtypes. Its efficacy is not restricted by co-receptor (e.g., R5, X4 and R5X4) specificity.
The mechanism of action of retrocyclins has been studied. Their effectiveness against HIV-1 results from the prevention of viral entry, and is correlated to their ability to bind CD4 and gp120 with high affinity. Surface plasmon resonance experiments revealed that retrocyclin-2's affinity (Kd) for gp120 was 9.4 nM and that its affinity for CD4 was 6.7 nM. Fluorescence confocal microscopy of T cells treated with fluorescent RC-101 (an active analogue of retrocyclin-1) revealed surface patches wherein retrocyclin and CD4 were co-localized, without evident peptide internalization. Additional information relevant to the activities and antiviral mechanisms of retrocyclins exists, and can be provided to interested parties after appropriate confidentiality agreements are established.

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All of our products are supplied as research grade (non GMP); therefore they are not for human use. The customer is responsible for all uses of the product in all cases.

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