Part:BBa_K3113051

CD63_Ser161_6xHis

To facilitate the purification of intact exosomes, we engineered the exosomal marker CD63 by integrating a polyhistidine repeat into the large extracellular loop of the tetraspanin. Based on SWISS-MODEL, a protein structure homology-modelling server, we were able to model CD63 and to search for sites within CD63 that are accessible.

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]

Usage and Biology

This part was designed to allow the purification of exosomes via affinity chromatography. The exosomal marker protein CD63 belongs to the family of tetraspanins and is therefore composed of four alpha-helical transmembrane domains with two extracellular loops. Both the N- and the C-terminus point towards the inside of exosomes, rendering terminal His-tagging useless for affinity purification of exosomes. Therefore, we innovatively fused a 6xHis-tag to an external loop of the exosomal marker CD63. Specifically, the 6 histidines were added after position Ser161 based on a structural model for CD63 generated with swissmodel.expasy.org and based on the structure of the related tetraspanin CD81 To our knowledge, Ni-NTA affinity chromatography has not been previously been used to purify exosomes, it has only been applied to other His-tagged membrane structures (Alves et al 2017). BBa_K3113051 is thus an improvement from iGEM 2018 XJTLU-China's part BBa_K2619003 , which just contains the human CD63 sequence.