Overview:
PRKAR1B is the type I-beta regulatory subunit of cyclic AMP-dependent protein kinase A (PKA) which is an essential enzyme in the cAMP signaling pathway. PKA holoenzyme is composed of 2 regulatory and 2 catalytic subunits and dissociates from the regulatory subunits upon binding of cAMP. PKA controls many biochemical events in the cell including regulation of metabolism, ion transport, and gene transcription. PKA undergoes a dramatic conformational change upon complex formation with the catalytic subunit (1). PRKAR1B subunits can dimerize through an N-terminal motif and this dimerization is necessary for binding to PKA anchoring proteins (AKAPs) and targeting of PKA to its site of action.
Gene Aliases:
PRKAR1
Genbank Number:
NM_002735
References:
1. Gullingsrud J, et al. Dynamic binding of PKA regulatory subunit RI alpha.Structure, 2006 Jan. PMID 16407073.2. Carlson, C R. et al: A kinase anchoring protein (AKAP) interaction and dimerization of the RIalpha and RIbeta regulatory subunits of protein kinase a in vivo by the yeast two hybrid system. J Mol Biol. 2003 Mar 28;327(3):609-18.
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所以一个细菌或病毒可以有很多的抗原。
若已进入细胞内。则先由巨噬细胞吞噬降解。并形成抗原-MHC复合体传送到表面。被辅助性T淋巴细胞识别和效应T淋巴细胞识别后。效应T淋巴细胞被激活。分解靶细胞。然后再由效应B细胞分泌的抗体进一步消灭病毒。
还有不清楚的么?
荚膜(capsule)是某些细菌在生长繁殖过程中分泌的一层黏液性物质,包围在细胞壁外,通常这种黏液层厚度小于0.2μm,成分是多糖或多肽,只有在营养丰富时或在动物体内,细菌才产生这种半抗原性质的黏液性物质。它具有保护菌体免受巨噬细胞等的捕捉和吞噬,因而具有抗吞噬抗消化、侵袭力强、与致病性关系密切等特点。像肺炎球菌、炭疽杆菌等都有这类荚膜。有些细菌的荚膜层较薄,小于0.2μm,称为微荚。
像链球菌的M蛋白、伤寒杆菌的Vi抗原、大肠杆菌的K抗原等都属于这类微荚膜。
请赐教!

