Link_domain_HAPLN_module_2; this link domain is found in the second link module of proteins similar to the vertebrate HAPLN (hyaluronan/HA and proteoglycan binding link) protein family which includes cartilage link protein. The link domain is a HA-binding domain. HAPLNs contain two contiguous link modules. Both link modules of cartilage link protein are involved in interaction with HA. In cartilage, a chondroitin sulfate proteoglycan core protein (CSPG) aggrecan forms cartilage link protein stabilized aggregates with HA. These aggregates contribute to the tissue's load bearing properties. Aggregates with other CSPGs substituting for aggregan may contribute to the structural integrity of many different tissues. Members of the vertebrate HAPLN gene family are physically linked adjacent to CSPG genes.
Feature 1:putative hyaluronan binding site [chemical binding site]
Evidence:
Comment:For the HAPLN link module 2 (G1 domain) these two putative HA- binding residues are not well conserved.
Comment:HA-binding residues were identified in TSG-6 and CD44 by site-directed mutagenesis.
Comment:These two HA-binding residues are found at equivalent sequence positions in TSG-6 and CD44 . None of the other HA-binding residues identified were found at equivalent sequence positions in the two proteins.
Jiyao W et al.(2023). "The conserved domain database in 2023.",