The function of LRRC23 is unknown. It is a member of the leucine-rich repeat family of proteins, which are known for participating in protein-protein interactions. Experimental evidence suggests that LRRC23 interacts with the CD28 protein in a pathway related to the immune system and development of regulatory T cells that control spontaneous autoimmune disease.[4]
Protein sequence
LRRC23 spans 343 residues containing two varieties of internally repeating sequence. Detected and aligned by RADAR,[5] the most abundant repeat is the leucine-rich repeat, repeating 9 times in bases 89-287. The other repeated sequence occurs twice in bases 3-36. The RADAR program output, below, summarizes the composition and location of all the repeats and aligns them for comparison against each other.
File:LRRC23 RADAR Internal Repeats.png
The human genome produces three known variants of LRRC23.[3] The largest splice variant, variant 3, contains 8 exons. Variants 1 and 2 use alternative first exons, and variant 2 excludes the seventh exon, giving it a total of seven exons making up the mRNA.
Protein structure
Although the actual structure of LRRC23 is unknown, comparison to the crystal structures of various similar proteins such as 2OMW A (e-value 1.00e-17) reveals a structure typical of other leucine-rich repeat proteins. Alternating beta sheets and coils create a spiraled peptide chain forming an arch shape with beta-sheets occupying the concave surface.[6]
The aligned structure of 2OMW_A with LRRC23 spans acids 72-272 of the LRRC23 protein. Conserved asparagines are highlighted in yellow, showing the regularity of spacing and repeat structure within. This model was generated using Cn3D software provided by NCBI.
↑Tzachanis D, Berezovskaya A, Nadler LM, Boussiotis VA (Feb 2002). "Blockade of B7/CD28 in mixed lymphocyte reaction cultures results in the generation of alternatively activated macrophages, which suppress T-cell responses". Blood. 99 (4): 1465–73. doi:10.1182/blood.V99.4.1465. PMID11830501.
↑Chang TT, Kuchroo VK, Sharpe AH (Feb 2002). "Role of the B7-CD28/CTLA-4 pathway in autoimmune disease". Current Directions in Autoimmunity. Current Directions in Autoimmunity. 5: 113–30. doi:10.1159/000060550. ISBN3-8055-7308-1. PMID11826754.
↑Salomon B, Lenschow DJ, Rhee L, Ashourian N, Singh B, Sharpe A, Bluestone JA (Apr 2000). "B7/CD28 costimulation is essential for the homeostasis of the CD4+CD25+ immunoregulatory T cells that control autoimmune diabetes". Immunity. 12 (4): 431–40. doi:10.1016/S1074-7613(00)80195-8. PMID10795741.
↑RADAR: European Molecular Biology Laboratory - European Bioinformatics Institute (EMBLE-EBI) Radar program: [1]
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