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. Author manuscript; available in PMC: 2011 Feb 1.
Published in final edited form as: Semin Immunol. 2010 Jan 6;22(1):25–33. doi: 10.1016/j.smim.2009.12.002

Figure 2.

Figure 2

Genomic organization and rearrangement of a mature VLR gene of sea lamprey. The germline VLR (gVLR) configuration with 5’ and 3’-encoding LRR genetic segments (top) contains an additional 13.2 kb of non-coding intervening sequence and lacks the key LRR modules, which are essential to the structure of functional VLR genes. The inserted LRR modules lie both 5’ and 3’ of gVLR. The VLR locus undergoes stepwise assembly (middle) via recombination between short stretches of nucleotide homology found at the junctions of various LRR modules. This process may occur on either (or both) strand(s) during replication and gradually replaces the intervening sequence with all the variable LRR segments. The end product of these recombination events (bottom) is a mature VLR locus capped with an invariant 5’ end of the LRRNT module, an invariant 3’ end of the LRRCT module and a variable number of LRR cassettes (each encoding 24 amino acids) that vary in number and sequence. The illustration is not drawn to scale.