# Anticalin

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**Anticalin proteins** are artificial [proteins](/source/Proteins) that are able to bind to [antigens](/source/Antigen), either to proteins or to [small molecules](/source/Small_molecules). They are not structurally related to [antibodies](/source/Antibodies), which makes them a type of [antibody mimetic](/source/Antibody_mimetic). Instead, they are derived from human [lipocalins](/source/Lipocalin) which are a family of naturally binding proteins. Anticalin proteins are being used in lieu of [monoclonal antibodies](/source/Monoclonal_antibodies), but are about eight times smaller with a size of about 180 [amino acids](/source/Amino_acid) and a mass of about 20 [kDa](/source/KDa).

The Anticalin technology is exclusively commercialized by Pieris Pharmaceuticals in [Freising](/source/Freising), [Germany](/source/Germany).[1] Anticalin is a registered trademark of Pieris.[citation needed]

## Properties

Anticalin proteins have better tissue penetration than antibodies and are stable at temperatures up to 70 °C. Unlike antibodies, they can be produced in bacterial cells like *[E. coli](/source/E._coli)* in large amounts.[2]

While antibodies can only be directed at [macromolecules](/source/Macromolecule) such as proteins and at small molecules ([haptens](/source/Hapten)) only if bound to macromolecules,[3] Anticalin proteins are able to selectively bind to small molecules as well.[citation needed]

They were mainly developed at the [Technical University of Munich](/source/Technical_University_of_Munich) and are currently used as research tools. [Diagnostic](/source/Diagnostic) and [therapeutic](/source/Therapeutic) applications, including the use for [targeted drug delivery](/source/Targeted_drug_delivery), are being aimed at.[4] The underlying technology was nominated for the [German Future Prize](/source/German_Future_Prize) in 2004.[5]

## Structure

Characteristic for Anticalin proteins is their barrel structure formed by eight antiparallel [β-strands](/source/%CE%92-strand) pairwise connected by loops and an attached [α-helix](/source/%CE%91-helix). The main structure of Anticalin proteins is identical to wild type lipocalins. Conformational deviations are primarily located in the four loops reaching in the ligand binding site.[2] [Mutagenesis](/source/Mutagenesis) of amino acids at the binding site allows for changing the affinity and selectivity.[citation needed]

## References

1. ["Pieris Pharmaceuticals, Inc."](http://www.pieris.com/). *Pieris Pharmaceuticals, Inc.*. Retrieved 16 June 2015.

1. Skerra A (June 2008). "Alternative binding proteins: anticalins - harnessing the structural plasticity of the lipocalin ligand pocket to engineer novel binding activities". *FEBS J.*. **275** (11): 2677–83. [doi:10.1111/j.1742-4658.2008.06439.x](https://doi.org/10.1111/j.1742-4658.2008.06439.x). [PMID 18435758](https://pubmed.ncbi.nlm.nih.gov/18435758). [S2CID 19992238](https://api.semanticscholar.org/CorpusID:19992238)

1. Mutschler, Ernst & Schäfer-Korting, Monika (2001). *Arzneimittelwirkungen* (in German). 8 ed. Stuttgart: Wissenschaftliche Verlagsgesellschaft. pp. 911f. ISBN 3-8047-1763-2.

1. Skerra, A (2002). ["Anticaline"](http://biologische-chemie.userweb.mwn.de/Publikationen/Skerra_BIOforum02.pdf) (in German). *BIOforum*. **4/2002**: 227–229. [Darmstadt](/source/Darmstadt): GIT Verlag.[dead link]

1. ["Deutscher Zukunftspreis 2004: Anticaline – Biopharmazeutische Wirkstoffe durch Protein-Design"](https://web.archive.org/web/20101208224617/http://www.deutscher-zukunftspreis.de/nominierter/anticalin%C2%AEe-biopharmazeutische-wirkstoffe-durch-protein-design) [German Future Prize 2004: Anticalins – Biopharmaceutical agents by protein design] (in German). Stifterverband für die Deutsche Wissenschaft. Archived from [the original](http://www.deutscher-zukunftspreis.de/nominierter/anticalin%C2%AEe-biopharmazeutische-wirkstoffe-durch-protein-design) on 8 December 2010. Retrieved 6 December 2010.

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