Way M, Sanders M, Chafel M, Tu Y H, Knight A, Matsudaira P
Whitehead Institute, Nine Cambridge Center, MA 02142, USA.
J Cell Sci. 1995 Oct;108 ( Pt 10):3155-62. doi: 10.1242/jcs.108.10.3155.
Scruin (alpha-scruin) is an actin bundling protein found in the acrosomal process of Limulus polyhemus sperm. We have cloned and sequenced a second scruin isoform from Limulus, beta-scruin, that is 67% identical to alpha-scruin. Northern and Southern analyses confirm that beta-scruin and alpha-scruin are encoded by distinct genes. The sequence of beta-scruin, like alpha-scruin, is organized into N- and C-terminal superbarrel domains that are characterized by a six-fold repeat of a 50 residue motif. Western analysis using rabbit polyclonal antisera specific for alpha- and beta-scruin indicate that beta-scruin, like alpha-scruin, is found in Limulus sperm but not blood or muscle. Both immunofluorescence microscopy and immunogold-EM localize beta-scruin within the acrosomal vesicle at the anterior of sperm but not in the acrosomal process. The function of beta-scruin in this membrane-bounded compartment that is devoid of actin is unknown. However, the location of beta-scruin together with the fact that it contains two putative beta-superbarrel structural folds, which are known to be catalytic domains in a number of proteins, suggests it may have a possible enzymatic role.
Scruin（α-Scruin）是一种肌动蛋白成束蛋白，存在于美洲鲎精子的顶体突起中。我们从美洲鲎中克隆并测序了第二种Scruin同工型，β-Scruin，它与α-Scruin的同源性为67%。Northern和Southern分析证实β-Scruin和α-Scruin由不同的基因编码。β-Scruin的序列与α-Scruin一样，被组织成N端和C端超桶结构域，其特征是一个50个残基基序的六重重复。使用针对α-Scruin和β-Scruin的兔多克隆抗血清进行的Western分析表明，β-Scruin与α-Scruin一样，存在于美洲鲎精子中，但不存在于血液或肌肉中。免疫荧光显微镜和免疫金电子显微镜都将β-Scruin定位在精子前部的顶体小泡内，而不是顶体突起中。β-Scruin在这个没有肌动蛋白的膜结合隔室中的功能尚不清楚。然而，β-Scruin的位置以及它包含两个假定的β-超桶结构折叠这一事实，已知这在许多蛋白质中是催化结构域，表明它可能具有潜在的酶促作用。
