Takahashi Akiyoshi, Yasuda Akikazu, Sower Stacia A, Kawauchi Hiroshi
Laboratory of Molecular Endocrinology, School of Fisheries Sciences, Kitasato University, Sanriku, Ofunato, Iwate 022-0101, Japan.
Gen Comp Endocrinol. 2006 Aug;148(1):79-84. doi: 10.1016/j.ygcen.2005.09.022. Epub 2005 Nov 14.
In gnathostomes, adrenocorticotropic hormone (ACTH), melanophore-stimulating hormones (MSHs), and beta-endorphin (beta-END) are derived from a common precursor, proopiomelanocortin. In sea lamprey, ACTH and two forms of MSHs are contained in independent precursors, proopiocortin (POC), and proopiomelanotropin (POM), respectively, together with a distinct beta-END. Here, we characterized products from POC and POM. An analysis of previously purified ACTH by mass spectrometry (MS) detected four peptides with a molecular weight of 6469.4, 6549.6, 6556.6, or 6636.1. The sequence analysis of an ACTH preparation following enzymatic and chemical cleavage revealed the presence of ACTH(1-59) and ACTH(1-60) corresponding to a molecular weight of 6469.4 and 6556.6, respectively, and of ACTH(1-59) and ACTH(1-60) modified at Ser(35) by a group having a mass of 80, giving the molecular weight 6549.6 and 6636.1, respectively. The modification could be due to phosphorylation based on the increase in molecular weight of 80. Analyses of frozen pituitary slices with MALDI-TOF MS detected several mass numbers corresponding to POC-derived peptides such as ACTH(1-60), modified ACTH(1-60), and (POC)beta-END, and those corresponding to POM-derived peptides such as MSH-A, MSH-B, and the C-terminal fragment of (POM)beta-END lacking a Met-enkephalin segment. The present results together with previous characterizations show that in sea lamprey pituitary the major products derived from POC in the PD by posttranslational processing are ACTH and beta-END as in gnathostomes. The posttranslational processing of POM in the PI is similar to that in gnathostomes in the sense of the occurrence of MSH, however, it differs in that beta-END is further cleaved, thus generating Met-enkephalin.
在颌口类动物中，促肾上腺皮质激素（ACTH）、促黑素细胞激素（MSHs）和β-内啡肽（β-END）均来源于一个共同的前体——阿黑皮素原。在海七鳃鳗中，ACTH和两种形式的MSHs分别包含在独立的前体中，即促阿片皮质素（POC）和促阿片黑素细胞刺激素（POM），同时还含有一种独特的β-END。在此，我们对POC和POM的产物进行了表征。通过质谱（MS）对先前纯化的ACTH进行分析，检测到四种分子量分别为6469.4、6549.6、6556.6或6636.1的肽段。对酶解和化学裂解后的ACTH制剂进行序列分析，结果显示存在分子量分别为6469.4和6556.6的ACTH(1-59)和ACTH(1-60)，以及在Ser(35)处被一个分子量为80的基团修饰的ACTH(1-59)和ACTH(1-60)，其分子量分别为6549.6和6636.1。基于分子量增加80，这种修饰可能是由于磷酸化所致。用基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）对冷冻垂体切片进行分析，检测到几个与POC衍生肽段相对应的质量数，如ACTH(1-60)、修饰的ACTH(1-60)和(POC)β-END，以及与POM衍生肽段相对应的质量数，如MSH-A、MSH-B和缺少甲硫氨酸脑啡肽片段的(POM)β-END的C末端片段。目前的结果与先前的表征共同表明，在海七鳃鳗垂体中，通过翻译后加工从POC衍生的主要产物与颌口类动物一样是ACTH和β-END。在PI中POM的翻译后加工在MSH出现方面与颌口类动物相似，然而，不同之处在于β-END会进一步裂解，从而产生甲硫氨酸脑啡肽。
