The domain within your query sequence starts at position 257 and ends at position 431; the E-value for the DUF21 domain shown below is 7.8e-39.

LQVIFISLLLCLSGMFSGLNLGLMALDPMELRIVQNCGTEKEKNYAKRIEPVRRQGNYLL
CSLLLGNVLVNTTLTILLDDIAGSGLVAVVVSTIGIVIFGEIVPQAICSRHGLAVGANTI
FLTKFFMMMTFPASYPVSKLLDCVLGQEIGTVYNREKLLEMLRVTDPYNDLVKEE

DUF21

DUF21
PFAM accession number:PF01595
Interpro abstract (IPR002550):

Proteins containing the ancient conserved domain protein/cyclin M (CNNM) are integral membrane proteins that are conserved from bacteria to humans. CNNM family members influence metal ion homeostasis through mechanisms that may not involve direct membrane transport of the ions. Structurally, CNNMs are complex proteins that contain an extracellular N-terminal domain preceding a transmembrane domain, a "Bateman module", which consists of two cystathionine- beta-synthase (CBS) domains, and a C-terminal cNMP (cyclic nucleotide monophosphate) binding domain [(PUBMED:15498024), (PUBMED:22399287), (PUBMED:27856537), (PUBMED:27899452)].

The CNNM transmembrane domain contains four hydrophobic regions. The second one is the shortest and the least hydrophobic, indicating that the second hydrophobic region might not be completely membrane-spanning, but instead forms a re-entrant loop. Hence, the CNNM integral membrane domain has been proposed to contain three full membrane-spanning regions and an additional re-entrant loop [(PUBMED:22399287)].

This is a PFAM domain. For full annotation and more information, please see the PFAM entry DUF21