Gao Z H, Zhong G
Laboratory of Biochemistry, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Gene. 1999 Mar 4;228(1-2):51-9. doi: 10.1016/s0378-1119(99)00007-4.
Calcineurin B (CnB) and calmodulin (CaM) are two structurally similar but functionally distinct 'EF-hand' Ca2+-binding proteins. CnB is the regulatory subunit of the CaM-stimulated protein phosphatase, calcineurin. CaM is a unique multifunctional protein that interacts with and modulates the activity of many target proteins. CnB and CaM are both required for the full activation of the phosphatase activity of calcineurin and are not interchangeable. The two proteins recognize distinct binding sites on calcineurin A subunit (CnA) and perform different functions. Phage-displayed peptide libraries (pIII and pVIII libraries) were screened with CnB and CaM to isolate peptides that could then be compared to determine if there were binding preferences of the two proteins. The Ca2+-dependent binding of phage-displayed peptides to CnB and CaM is specifically blocked by synthetic peptides derived from the CnB-binding domain of CnA and the CaM-binding domain of myosin light chain kinase respectively. Both CnB- and CaM-binding peptides have a high content of tryptophan and leucine, but CnB-binding peptides are more hydrophobic than CaM-binding peptides. CnB-binding peptides are negatively charged with clusters of hydrophobic residues rich in phenylalanine, whereas the CaM-binding peptides are positively charged and often contain an Arg/Lys-Trp motif. The binding preferences identified with peptide libraries are consistent with the features of the CnB-binding domains of all CnA isoforms and the CaM-binding domains of CaM targets.
钙调神经磷酸酶B（CnB）和钙调蛋白（CaM）是两种结构相似但功能不同的“EF手型”钙离子结合蛋白。CnB是钙调神经磷酸酶（一种受CaM刺激的蛋白磷酸酶）的调节亚基。CaM是一种独特的多功能蛋白，它与许多靶蛋白相互作用并调节其活性。CnB和CaM都是钙调神经磷酸酶磷酸酶活性完全激活所必需的，且二者不可互换。这两种蛋白识别钙调神经磷酸酶A亚基（CnA）上不同的结合位点并执行不同功能。用CnB和CaM筛选噬菌体展示肽库（pIII和pVIII库），以分离出可随后进行比较的肽，从而确定这两种蛋白是否存在结合偏好。噬菌体展示肽与CnB和CaM的钙离子依赖性结合分别被源自CnA的CnB结合结构域和肌球蛋白轻链激酶的CaM结合结构域的合成肽特异性阻断。CnB结合肽和CaM结合肽都富含色氨酸和亮氨酸，但CnB结合肽比CaM结合肽更具疏水性。CnB结合肽带负电荷，富含苯丙氨酸的疏水残基成簇，而CaM结合肽带正电荷，且通常含有Arg/Lys-Trp基序。用肽库确定的结合偏好与所有CnA同工型的CnB结合结构域以及CaM靶标的CaM结合结构域的特征一致。
