This is an extracellular cadherin (EC) domain which can be found at the N-terminal region of Protocadherin 15 (Pcdh15). Pcdh15 features exceptionally long extracellular domains containing 11 ECs [1]. These repeats are structurally similar, but not identical in sequence, often featuring linkers with conserved calcium-binding sites that confer mechanical strength to them [2].

1: Structure of a force-conveying cadherin bond essential for inner-ear mechanotransduction. Sotomayor M, Weihofen WA, Gaudet R, Corey DP; Nature. 2012;492:128-132. PMID:23135401

2: A Partial Calcium-Free Linker Confers Flexibility to Inner-Ear Protocadherin-15. Powers RE, Gaudet R, Sotomayor M; Structure. 2017;25:482-495. PMID:28238533