Koehn R K, Newell R I, Immermann F
Proc Natl Acad Sci U S A. 1980 Sep;77(9):5385-9. doi: 10.1073/pnas.77.9.5385.
The product of the Lap locus in the marine bivalve Mytilus edulis is a neutral, membrane-associated aminopeptidase that is primarily localized on intestinal microvilli and in digestive cell lysosomes. Natural populations are genetically differentiated at the Lap locus between areas of differing salinity. A steep (0.55-0.15) allele frequency cline connects differentiated populations between the Atlantic Ocean and Long Island Sound. We demonstrate an annual gene flow/mortality cycle in cline populations whereby gene frequencies after mortality are correlated with salinity and enzyme activity. The cline is spatially and temporally unstable in immigrants, but stable in residents after mortality. Mortality is nonrandom with regard to the Lap locus; genotype-dependent properties of the aminopeptidase enzyme apparently led to a differential rate of the utilizaiton of nutrient reserves because selected genotypes exhibited an increased rate of tissue weight loss. Aminopeptidase genotypes are differentially adapted to different temperatures and salinities, which provides a mechanism for the relationship among biochemical, physiological, and population phenotypes.
海洋双壳贝类贻贝中Lap位点的产物是一种中性的、与膜相关的氨肽酶，主要定位于肠道微绒毛和消化细胞溶酶体中。在盐度不同的区域，Lap位点的自然种群在基因上存在差异。一条陡峭的（0.55 - 0.15）等位基因频率渐变群连接了大西洋和长岛海峡之间的分化种群。我们证明了渐变群种群中存在年度基因流动/死亡率周期，即死亡率后的基因频率与盐度和酶活性相关。渐变群在移民中在空间和时间上不稳定，但在死亡率后的本地种群中稳定。关于Lap位点，死亡率是非随机的；氨肽酶的基因型依赖性特性显然导致了营养储备利用速率的差异，因为选定的基因型表现出组织重量损失速率增加。氨肽酶基因型对不同温度和盐度有不同的适应性，这为生化、生理和种群表型之间的关系提供了一种机制。
