雞肌肉蛋白-旋光抑制素（TnI）多態性研究

吳欽翔⁽¹⁾ 劉英明⁽¹⁾ 張秀鑾⁽²⁾ 鍾秀枝⁽²⁾ 林德育⁽²⁾ 吳明哲⁽²⁾

⁽¹⁾國立中興大學動物系 ⁽²⁾行政院農業委員會畜產試驗所

旋光抑制素（TnI）為肌肉纖維內重要的肌絲蛋白，可調節肌肉收縮活性與穩定肌纖維結構之功能。本研究之主要目的在探討不同品系間雞肉內肌絲蛋白分子多態性表現之差異性。試驗組雞隻為畜產試驗所選育之8週齡近親品系土雞（L7、L9、L11、L12）、二元雜交雞（PS）及公土雞與配絲羽（CW）或黑羽（CB）烏骨母雞之雜交品系，而對照組雞隻則採用坊間一般有色雞隻。動物犧牲後取下大胸肌，隨後去除細胞膜的結構製備成去膜肌纖維，以降低水解蛋白分解肌絲蛋白分子的酵素活性。同時應用聚丙醯凝膠蛋白電泳（SDS-PAGE）分離不同分子大小之肌肉蛋白，並且利用分子專一性肌絲蛋白抗體辨識肌肉中特定的蛋白分子。試驗雞隻大胸肌纖維內雖均表現兩種不同分子大小的旋光抑制素（分子量分別為23.2與22.6 kD），但不同品系間肌肉纖維內之分子同分異構物分佈比例，則有顯著的差異（P<0.05）。L7、L9、L11、L12、PS、CW與CB雞隻之肌肉纖維內高分子量TnI（23.2 kD）表現比例分別為60.4%、68.7%、81.1%、71.8%、26.6%%、40%與57.1%，顯示L7、L9、L11、L12四個土雞近親品系肌肉中具有高分子量TnI為主，而PS、CW與CB品系雞隻肌肉中具有低分子量TnI為主；而對照組坊間有色雞隻之肌肉纖維內則僅表現高分子量TnI。結果顯示不同品系間肌肉纖維內之旋光抑制素的表現有品系差異存在。

關鍵語：旋光抑制素（TnI）、多態性表現、台灣土雞。

POLYMORPHIC EXPRESSION OF MYOFILAMENT PROTEIN TROPONIN I IN
THE PECTORALIS MAJOR MUSCLE OF DOMESTIC CHICKENS

K-S Goh(1), Y. M. Liou(1), H. L. Chang(2), H. C. Chung(2), D. Y. Lin(2) and M. C. Wu(2)

(1)National Chung-Hsing University (2)Taiwan Livestock Research Institute, Council of Agriculture

Troponin I (TnI) is a regulatory protein of myofilament protein. TnI regulates the contractile activities of muscle and stabilizes the structure of myofilaments. The aim of this study was to investigate if strain-dependent differences of muscle protein expression exist in skeletal muscle of various domestic chickens. Taiwan country chicken inbred lines (L12, L7, L11 and L9), and their hybrid (PS) as well as Silkie-Country hybrids (CW and CB) provided from Taiwan livestock Research Institute (TLRI) were used along with several commercial strains of colored chickens. The Pectoralis Major muscle taken from experimental animals were prepared for chemically skinned muscle fibers in which membranous structures of muscle fibers were removed. This treatment of skinning would decrease the proteinase activity and prevent proteolysis of muscle proteins. SDS polyacrylamide gel electrophoresis in combination with immuno-blotting method was used to identify specific myofilament proteins in muscle fibers. Results obtained showed that two different molecular size (MW: Heavy/23.2 kD and Light/22.6 kD) of Troponin I (TnI) expressed in the Pectoralis Major of all chickens from TLRI. However, the expressed ratios of these two TnI isozymes are different in muscle fibers of different strains. The expression of the heavy TnI isozyme in muscle fibers is greater for the strains L12 (71.7%), L7 (60.3%), L11 (81.1%) and L9 (68.7%) than for strains PS (26.6%), CW (40%) and CB (57.1%). Interestingly, only one band of high molecular weight of TnI (23.2 kD) was found in other originated chickens. Thus, polymorphic expression of myofilament proteins in chicken muscles could be strain-specific, and that might provide a means for further characterizing muscle differences between a variety of domestic chickens.

Key Words: Troponin I (TnI), Polymorphic expression, Taiwan country chicken.