For websites with multiple subdomains, each subdomain must have its own robots.txt file. A domain holder may provide an infinite number of subdomains in their domain. DNA-binding domain consists of two subdomains. Misspelled URLs or the use of subdomains are common tricks used by phishers. Equally two subdomains of the same domain may be hosted together. Each domain is a product of two subdomains that possess common structural motifs. The extracellular domain contains four subdomains (I-IV). Only the site's highest-level domain is recorded, aggregating any subdomains. Registrations of subdomains are processed via accredited registrars worldwide. An example of the EA domain and subdomains is in the image on the right. Upon activation, they assign proteins to specific membrane subdomains where they participate in signaling. Individual ccTLDs may have varying requirements and fees for registering subdomains. Existing registrations in these subdomains can continue to be renewed. Biomolecular condensates are a class of non-membrane bound organelles and organelle subdomains. Gelsolin is an 82-kD protein with six homologous subdomains, referred to as S1-S6.