Evidence for species-specificity of mammalian cardiac contractile proteins

54 PIlOSPII0-DEPtIOSP}IORYLATION OF CARDIAC SARCOLE},INA. P . V . S u ] a k h e and P . J . St. Louis. D~partment of Physiology, College of M~dic~ne, University of

Saskatchewan, 5askatoon, Canada, S7N 0W0. }{ydroxy]amine-insensitive incorporation of [T-32p] of ATP into saree]emma (SL, guinea pig heart ventricles) catalyzed by endogenous (En) or exogenous (Ex) protein kfnase (PK) was mainly due to phosphory]ation of t]nee SL proteins: 48K-, 23K- and ]SK-da]ton. The degree of p]}osphorylation of 48K- and 23K-proteins amounted to 38 and 37 respectively with FnPK ~md ]62 and 692 pmo]cs/mg/5 rain with ExPK (catalytic subunit of b~wilw muscle PK). P l i r i f f e d phosphoprote~n phosphatase (PPase, i-abbit ]ivcr) dci)]~o~q)]a)ry]alods/trcolemma] phosphoprotedns (40% d~:phosphory]i~ti{~] wilh 0.2 ]~g PPase ~n ]0 rain at 30~ ExPK-oatalyzed phosp]}ory]ation in{ c{,,l:;,,d t h e ~-ate o f :~nd t o t a l o:roteins i n tl~e r ~ ' ; ; u ] a t i o n o f Ca 2+ t r a n ~ q ) o r t in SL by c y c ] S c AbIP w i ] l be d i s c u s s e d . [ , % l p p o r t e d by a g r a n t f r o m S a s k a t c l l c w n n H e a r t Fom~d;tt:ion ( S u ] a k h e ) ~md l ~ , o s t - ( h ) c t t ~ r a ] f e l ] o w ~ d ~ i p a w a r d fr,/m Cnml(liam H c ; t r t F o ~ m d a t f i o n ( S t . L o u i s ) ] .

EVID ~LI
P~)TE_~S. B. Swynghedaur~, G, Befson, C. Delcayre, C. Klotz, J.J. L@ger, G. Laca~zbe, N. Thiera ~md K. Sch~-martz. G 127, INSET4.1, Fac. de MC~lecine (rue des Sts-POres), Paris, France. Y~mmmlian heart, a tissue ccm~[x]sed of a single t_ype of fiber, is an ideal model for phylcxjenic studies. ~ r e o v e r it is easy to correlate t]le biochemical results with the speed of shortening of each heart since this parameter changes from one mammalian species to the other (the smallest the heart, the faster the oontractJon) ) (i) ~9]osJn. The ATPase measured in a steady state is inversely related to heart weight (mice> rat> guinea p i g > rabbit~ dog~/ pig, sheep and human). Similar results have been observed with the initial burst - Several ~mino acids substitutions have been shown in the semuence of the N-terminal peptide of bovine and hmmml light chains LCI (non phosphorylated LC) - The antigenic oonfiquration of cardiac HFN and myosins from rat, pig, human a.nd mice is markedly different as shown by the micro-complement fixation technique- (ii) Tropon~fosin (TM), Troponin inhibitory factor (~I) Small hearts only contain the cioz TM, whereas the bigger ones contain both an 0<~ and ac<~ TM. The activating effect of the ~(c~ TM on actomyosin ATPase differs from that of the 0( ~ TM. The charge of TNI is more negative in rat and mice that in bigger animals, but their

phosphate content and phosphorylating capacity is the same.