Determinants of antimicrobial activity and salt-resistance of defensin

人β防御素(HBD)-3对革兰氏阴性菌和革兰氏阳性菌均有较强的抗盐抗菌活性，而其他HBD只对革兰氏阴性菌有抗菌活性，在盐存在下其抗菌活性减弱。我们推测，这些特征是由于HBD-3的COOH-末端有两个精氨酸残基，而其他HBD-3没有涉及到。为了进行研究，我们命名了HBD-3的两个重组突变体：Desr HBD-3，其中这两个精氨酸残基从HBD-3中删除，NRR-HBD-3中，这两个精氨酸残基从COOH端移动到NH2端，并对它们的抗菌活性和耐盐性进行了研究。结果表明，为了保持HBD-3的活性和耐盐性，这两个精氨酸残基需要存在于COOH-末端。

Human β-defensin (HBD) -3 has potent and salt-resistant antimicrobial activity against both gram-negativeand gram positive bacteria and this activity, while other HBDs possess antimicrobial activity against only gram-negative strains and it is attenuated under salt existence. We hypothesized that these characteristics are due to two arginine residues in the COOH-terminal of HBD-3 which is not involved in other HBD-3. To investigate, we designated two recombinant mutants of HBD-3; desR HBD-3 in which these two arginine residues were deleted from HBD-3 and NRR-HBD-3 in which these two arginine residues were shifted from COOH-terminal to NH2-terminal and esxamined their antimicrobial activities and salt-resistance. The results showed that these two argine residues are required to exist in the COOH-terminal in order to maintain the activity and salt-resistance of HBD-3.