Defensin, alpha 1

Defensin, alpha 1 also known as human alpha defensin 1,  human neutrophil peptide 1 (HNP-1) or neutrophil defensin 1 is a human is_associated_with::protein that is encoded by the DEFA1 is_associated_with::gene. Human alpha defensin 1 belongs to the is_associated_with::alpha defensin family of is_associated_with::antimicrobial is_associated_with::peptides.

Function
is_associated_with::Defensins are a family of microbicidal and cytotoxic peptides thought to be involved in host defense. They are abundant in the granules of is_associated_with::neutrophils and also found in the epithelia of mucosal surfaces such as those of the intestine, respiratory tract, urinary tract, and vagina. Members of the defensin family are highly similar in protein sequence and distinguished by a conserved cysteine motif. Several is_associated_with::alpha defensin genes are clustered on is_associated_with::chromosome 8. The protein encoded by this gene, defensin, alpha 1, is found in the microbicidal granules of neutrophils and likely plays a role in phagocyte-mediated host defense. It differs from the defensins, alpha 2 and alpha 3 by only one amino acid.

Biosynthesis
HNPs are generated as 94 is_associated_with::amino acids preproHNPs, which are co-translationally cleaved to 75 is_associated_with::amino acids pro-peptides with a N-terminal prosegment having a negative charge that neutralizes the highly positively charged C terminal peptide. Processing of proHNPs occurs mainly in late promyelocytes, where the 75 is_associated_with::amino acids proHNPs are cleaved to a 56 is_associated_with::amino acids intermediate form and onward to 29-30 is_associated_with::amino acids mature peptides designated HNPs. Cationic 29-30 is_associated_with::amino acids HNPs associate with the negatively charged proteoglycan serglycin and translocate to azurophil granules. At later stages of granulocytic differentiation in which HNP expression peaks (i.e. myelocytes and metamyelocytes), proHNPs are not cleaved, rendering the peptides overall neutral. This prevents binding to serglycin and most proHNP is accordingly secreted into the bone marrow plasma although some is retained in specific granules.