Class B scavenger receptor type 1 (SRB1) serves as a high-density lipoprotein (HDL) receptor essential for HDL metabolism, and plays vital roles in innate immunity. In this study, the turbot (Scophthalmus maximus) SRB1 was cloned and characterized. The gene structure consists of a coding region of 1,527 bp nucleotides dividing into 13 exons and 12 introns. Such genome structure is highly conserved among teleost fishes. The deduced SRB1 encodes 508 amino acids that mainly has a CD36 transmembrane domain. Tissue distribution of SRB1 showed the lowest expression in liver, while the highest expression was found in intestine. Significantly down-regulation pattern of SmSRB1 expression in intestine was shared after infection with Vibrio anguillarum and Streptococcus iniae. Brach and site models in CODEML program showed that SmSRB1 underwent a conservative evolutionary and three potential positive selected sites 470K, 496E, and 501Y were detected, which require further investigation and confirmation using base-editing technologies. Subcellular localization demonstrated that turbot SRB1 was distributed in the membrane and cytoplasm. rSmSRB1 showed binding ability in vitro to both bacteria, LPS, PGN, LTA and virus. Protein-protein interaction network agrees the function of SRB1 as lipoprotein receptor, which requires further investigation. Our results indicated SmSRB1 might act as co-receptors to TLRs and NLRs to modulate the immune response to pathogens. Further studies should pay attention to evaluate the specific co-receptor for SRB1 in recognition of different pathogens and selective mechanisms involved.

B类清道夫受体1型（SRB1）是HDL代谢必不可少的高密度脂蛋白（HDL）受体，在先天免疫中起着至关重要的作用。在这项研究中，大菱t（Scophthalmus maximus）SRB1被克隆并鉴定。基因结构由1,527 bp核苷酸的编码区组成，分为13个外显子和12个内含子。这样的基因组结构在硬骨鱼类中高度保守。推导的SRB1编码508个氨基酸，主要具有CD36跨膜结构域。SRB1的组织分布在肝脏中最低表达，而在肠道中最高表达。感染弧菌和链球菌感染后，肠道中SmSRB1的表达显着下调。Brach和站点模型在CODEML程序中显示，SmSRB1经历了保守的进化，并检测到三个潜在的阳性选定站点470K，496E和501Y，这需要使用基础编辑技术进行进一步调查和确认。亚细胞定位表明大菱turbo SRB1分布在膜和细胞质中。rSmSRB1具有体外结合能力对细菌，LPS，PGN，LTA和病毒均有效。蛋白质-蛋白质相互作用网络同意SRB1作为脂蛋白受体的功能，这需要进一步研究。我们的结果表明SmSRB1可能充当TLR和NLR的共受体，以调节对病原体的免疫应答。进一步的研究应注意评估SRB1的特异性共受体，以识别不同的病原体和涉及的选择性机制。