Defensin Beta2 (B-D2) is also referred as Skin-antimicrobial peptide 1 (SAP 1). Denfensin Beta 2 is coded by DEFB4 gene and human defensin Beta-2 is cationic low molecular weight and cysteine rich antimicrobial peptide discovered in lesional skin. The human defensin Beta 2 consists of 64 amino acids in its primary structure. It is monomeric at less than or equal to 2.4 mM concentrations. Its structure is amphiphilic with non-uniform surface distribution of positive charge. Defensin Beta 2 also contains various structural elements which includes antiparallel Beta Sheet with 2 and 3 in beta hairpin conformation and Triple-stranded. The other structural determination for defensin Beta 2 depends on the used technique. Alpha helix can be observed by X ray crystallography at the C terminal end of the protein whereas it does not appear when NMR is used.

Defensins together form a family of cytotoxic peptides and microbicidal peptides which are formed by the neutrophils. Number of epithelial cells produce Human defensive beta 2 which display antimicrobial activity against Gram Negative and Candida species but not for Gram positive S.aureus. all of the defensin members contain similar protein sequence. Locally Defensin Beta 2 are regulated by inflammation. Beta defensive 2 also contribute in frequency of Gram-negative bacteria in lung tissues and skin. Stimulation of the epithelial cells is caused by the contact of microorganisms like P.aeruginosa or by TNF-alpha and IL-1 beta cytokines and lead to production of human defensin beta-2. Human defensin beta-2 plays a big role respiratory tract skin defensive system and protect the surfaces from infection. This is the major reason which makes it rare situation of Gram-negative lung and skin infection. This protein does not have activity on Gram-positive bacteria but one of the study displays a synergy between human defensin beta 2 and other proteins.