Center for Biomolecular Materials Spectroscopy, Laboratory for Chemical Physics, New York University, 345 East 24th Street, New York, New York 10010, USA.
Biomacromolecules. 2009 Dec 14;10(12):3298-305. doi: 10.1021/bm900893f.
Several biomineralization proteins that exhibit intrinsic disorder also possess sequence regions that are homologous to nonmineral associated folded proteins. One such protein is the amorphous calcium carbonate binding protein (ACCBP), one of several proteins that regulate the formation of the oyster shell and exhibit 30% conserved sequence identity to the acetylcholine binding protein sequences. To gain a better understanding of the ACCBP protein, we utilized bioinformatic approaches to identify the location of disordered and folded regions within this protein. In addition, we synthesized a 50 AA polypeptide, ACCN, representing the N-terminal domain of the mature processed ACCBP protein. We then utilized this polypeptide to determine the mineralization activity and qualitative structure of the N-terminal region of ACCBP. Our bioinformatic studies indicate that ACCBP consists of a ten-stranded beta-sandwich structure that includes short disordered sequence blocks, two of which reside within the primarily helical and surface-accessible ACCN sequence. Circular dichroism studies reveal that ACCN is partially disordered in solution; however, ACCN can be induced to fold into an alpha helix in the presence of TFE. Furthermore, we confirm that the ACCN sequence is multifunctional; this sequence promotes radial calcite polycrystal growth on Kevlar threads and forms supramolecular assemblies in solution that contain amorphous-appearing deposits. We conclude that the partially disordered ACCN sequence is a putative site for mineralization activity within the ACCBP protein and that the presence of short disordered sequence regions within the ACCBP fold are essential for function.
几种具有内在无序性的生物矿化蛋白也具有与非矿化相关的折叠蛋白同源的序列区域。其中一种蛋白是无定形碳酸钙结合蛋白（ACCBP），它是几种调节牡蛎壳形成的蛋白之一，与乙酰胆碱结合蛋白序列具有 30%的保守序列同一性。为了更好地理解 ACCBP 蛋白，我们利用生物信息学方法来确定该蛋白中无序和折叠区域的位置。此外，我们合成了一个 50 个氨基酸的多肽 ACCN，代表成熟加工后的 ACCBP 蛋白的 N 端结构域。然后，我们利用该多肽来确定 ACCBP N 端区域的矿化活性和定性结构。我们的生物信息学研究表明，ACCP 由一个由十个β-折叠组成的三明治结构组成，其中包括短的无序序列块，其中两个位于主要的螺旋和表面可及的 ACCN 序列内。圆二色性研究表明，ACCN 在溶液中部分无序；然而，在 TFE 的存在下，ACCN 可以诱导折叠成α螺旋。此外，我们证实了 ACCN 序列具有多功能性；该序列促进 Kevlar 线的方解石多晶生长，并在溶液中形成具有无定形外观沉积物的超分子组装。我们得出结论，部分无序的 ACCN 序列是 ACCBP 蛋白中矿化活性的一个假定位点，而 ACCBP 折叠中短的无序序列区域的存在对于功能至关重要。
